From: Jeff Xu jeffxu@chromium.org
This is V9 version, with removing MAP_SEALABLE and PROT_SEAL from mmap(), adding perfrmance benchmark and a test to demo the sealing of read-only memory segment of elf mapping.
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This patchset proposes a new mseal() syscall for the Linux kernel.
In a nutshell, mseal() protects the VMAs of a given virtual memory range against modifications, such as changes to their permission bits.
Modern CPUs support memory permissions, such as the read/write (RW) and no-execute (NX) bits. Linux has supported NX since the release of kernel version 2.6.8 in August 2004 [1]. The memory permission feature improves the security stance on memory corruption bugs, as an attacker cannot simply write to arbitrary memory and point the code to it. The memory must be marked with the X bit, or else an exception will occur. Internally, the kernel maintains the memory permissions in a data structure called VMA (vm_area_struct). mseal() additionally protects the VMA itself against modifications of the selected seal type.
Memory sealing is useful to mitigate memory corruption issues where a corrupted pointer is passed to a memory management system. For example, such an attacker primitive can break control-flow integrity guarantees since read-only memory that is supposed to be trusted can become writable or .text pages can get remapped. Memory sealing can automatically be applied by the runtime loader to seal .text and .rodata pages and applications can additionally seal security critical data at runtime. A similar feature already exists in the XNU kernel with the VM_FLAGS_PERMANENT [3] flag and on OpenBSD with the mimmutable syscall [4]. Also, Chrome wants to adopt this feature for their CFI work [2] and this patchset has been designed to be compatible with the Chrome use case.
Two system calls are involved in sealing the map: mmap() and mseal().
The new mseal() is an syscall on 64 bit CPU, and with following signature:
int mseal(void addr, size_t len, unsigned long flags) addr/len: memory range. flags: reserved.
mseal() blocks following operations for the given memory range.
1> Unmapping, moving to another location, and shrinking the size, via munmap() and mremap(), can leave an empty space, therefore can be replaced with a VMA with a new set of attributes.
2> Moving or expanding a different VMA into the current location, via mremap().
3> Modifying a VMA via mmap(MAP_FIXED).
4> Size expansion, via mremap(), does not appear to pose any specific risks to sealed VMAs. It is included anyway because the use case is unclear. In any case, users can rely on merging to expand a sealed VMA.
5> mprotect() and pkey_mprotect().
6> Some destructive madvice() behaviors (e.g. MADV_DONTNEED) for anonymous memory, when users don't have write permission to the memory. Those behaviors can alter region contents by discarding pages, effectively a memset(0) for anonymous memory.
The idea that inspired this patch comes from Stephen Röttger’s work in V8 CFI [5]. Chrome browser in ChromeOS will be the first user of this API.
Indeed, the Chrome browser has very specific requirements for sealing, which are distinct from those of most applications. For example, in the case of libc, sealing is only applied to read-only (RO) or read-execute (RX) memory segments (such as .text and .RELRO) to prevent them from becoming writable, the lifetime of those mappings are tied to the lifetime of the process.
Chrome wants to seal two large address space reservations that are managed by different allocators. The memory is mapped RW- and RWX respectively but write access to it is restricted using pkeys (or in the future ARM permission overlay extensions). The lifetime of those mappings are not tied to the lifetime of the process, therefore, while the memory is sealed, the allocators still need to free or discard the unused memory. For example, with madvise(DONTNEED).
However, always allowing madvise(DONTNEED) on this range poses a security risk. For example if a jump instruction crosses a page boundary and the second page gets discarded, it will overwrite the target bytes with zeros and change the control flow. Checking write-permission before the discard operation allows us to control when the operation is valid. In this case, the madvise will only succeed if the executing thread has PKEY write permissions and PKRU changes are protected in software by control-flow integrity.
Although the initial version of this patch series is targeting the Chrome browser as its first user, it became evident during upstream discussions that we would also want to ensure that the patch set eventually is a complete solution for memory sealing and compatible with other use cases. The specific scenario currently in mind is glibc's use case of loading and sealing ELF executables. To this end, Stephen is working on a change to glibc to add sealing support to the dynamic linker, which will seal all non-writable segments at startup. Once this work is completed, all applications will be able to automatically benefit from these new protections.
In closing, I would like to formally acknowledge the valuable contributions received during the RFC process, which were instrumental in shaping this patch:
Jann Horn: raising awareness and providing valuable insights on the destructive madvise operations. Liam R. Howlett: perf optimization. Linus Torvalds: assisting in defining system call signature and scope. Theo de Raadt: sharing the experiences and insight gained from implementing mimmutable() in OpenBSD.
MM perf benchmarks ================== This patch adds a loop in the mprotect/munmap/madvise(DONTNEED) to check the VMAs’ sealing flag, so that no partial update can be made, when any segment within the given memory range is sealed.
To measure the performance impact of this loop, two tests are developed. [8]
The first is measuring the time taken for a particular system call, by using clock_gettime(CLOCK_MONOTONIC). The second is using PERF_COUNT_HW_REF_CPU_CYCLES (exclude user space). Both tests have similar results.
The tests have roughly below sequence: for (i = 0; i < 1000, i++) create 1000 mappings (1 page per VMA) start the sampling for (j = 0; j < 1000, j++) mprotect one mapping stop and save the sample delete 1000 mappings calculates all samples.
Below tests are performed on Intel(R) Pentium(R) Gold 7505 @ 2.00GHz, 4G memory, Chromebook.
Based on the latest upstream code: The first test (measuring time) syscall__ vmas t t_mseal delta_ns per_vma % munmap__ 1 909 944 35 35 104% munmap__ 2 1398 1502 104 52 107% munmap__ 4 2444 2594 149 37 106% munmap__ 8 4029 4323 293 37 107% munmap__ 16 6647 6935 288 18 104% munmap__ 32 11811 12398 587 18 105% mprotect 1 439 465 26 26 106% mprotect 2 1659 1745 86 43 105% mprotect 4 3747 3889 142 36 104% mprotect 8 6755 6969 215 27 103% mprotect 16 13748 14144 396 25 103% mprotect 32 27827 28969 1142 36 104% madvise_ 1 240 262 22 22 109% madvise_ 2 366 442 76 38 121% madvise_ 4 623 751 128 32 121% madvise_ 8 1110 1324 215 27 119% madvise_ 16 2127 2451 324 20 115% madvise_ 32 4109 4642 534 17 113%
The second test (measuring cpu cycle) syscall__ vmas cpu cmseal delta_cpu per_vma % munmap__ 1 1790 1890 100 100 106% munmap__ 2 2819 3033 214 107 108% munmap__ 4 4959 5271 312 78 106% munmap__ 8 8262 8745 483 60 106% munmap__ 16 13099 14116 1017 64 108% munmap__ 32 23221 24785 1565 49 107% mprotect 1 906 967 62 62 107% mprotect 2 3019 3203 184 92 106% mprotect 4 6149 6569 420 105 107% mprotect 8 9978 10524 545 68 105% mprotect 16 20448 21427 979 61 105% mprotect 32 40972 42935 1963 61 105% madvise_ 1 434 497 63 63 115% madvise_ 2 752 899 147 74 120% madvise_ 4 1313 1513 200 50 115% madvise_ 8 2271 2627 356 44 116% madvise_ 16 4312 4883 571 36 113% madvise_ 32 8376 9319 943 29 111%
Based on the result, for 6.8 kernel, sealing check adds 20-40 nano seconds, or around 50-100 CPU cycles, per VMA.
In addition, I applied the sealing to 5.10 kernel: The first test (measuring time) syscall__ vmas t tmseal delta_ns per_vma % munmap__ 1 357 390 33 33 109% munmap__ 2 442 463 21 11 105% munmap__ 4 614 634 20 5 103% munmap__ 8 1017 1137 120 15 112% munmap__ 16 1889 2153 263 16 114% munmap__ 32 4109 4088 -21 -1 99% mprotect 1 235 227 -7 -7 97% mprotect 2 495 464 -30 -15 94% mprotect 4 741 764 24 6 103% mprotect 8 1434 1437 2 0 100% mprotect 16 2958 2991 33 2 101% mprotect 32 6431 6608 177 6 103% madvise_ 1 191 208 16 16 109% madvise_ 2 300 324 24 12 108% madvise_ 4 450 473 23 6 105% madvise_ 8 753 806 53 7 107% madvise_ 16 1467 1592 125 8 108% madvise_ 32 2795 3405 610 19 122% The second test (measuring cpu cycle) syscall__ nbr_vma cpu cmseal delta_cpu per_vma % munmap__ 1 684 715 31 31 105% munmap__ 2 861 898 38 19 104% munmap__ 4 1183 1235 51 13 104% munmap__ 8 1999 2045 46 6 102% munmap__ 16 3839 3816 -23 -1 99% munmap__ 32 7672 7887 216 7 103% mprotect 1 397 443 46 46 112% mprotect 2 738 788 50 25 107% mprotect 4 1221 1256 35 9 103% mprotect 8 2356 2429 72 9 103% mprotect 16 4961 4935 -26 -2 99% mprotect 32 9882 10172 291 9 103% madvise_ 1 351 380 29 29 108% madvise_ 2 565 615 49 25 109% madvise_ 4 872 933 61 15 107% madvise_ 8 1508 1640 132 16 109% madvise_ 16 3078 3323 245 15 108% madvise_ 32 5893 6704 811 25 114%
For 5.10 kernel, sealing check adds 0-15 ns in time, or 10-30 CPU cycles, there is even decrease in some cases.
It might be interesting to compare 5.10 and 6.8 kernel The first test (measuring time) syscall__ vmas t_5_10 t_6_8 delta_ns per_vma % munmap__ 1 357 909 552 552 254% munmap__ 2 442 1398 956 478 316% munmap__ 4 614 2444 1830 458 398% munmap__ 8 1017 4029 3012 377 396% munmap__ 16 1889 6647 4758 297 352% munmap__ 32 4109 11811 7702 241 287% mprotect 1 235 439 204 204 187% mprotect 2 495 1659 1164 582 335% mprotect 4 741 3747 3006 752 506% mprotect 8 1434 6755 5320 665 471% mprotect 16 2958 13748 10790 674 465% mprotect 32 6431 27827 21397 669 433% madvise_ 1 191 240 49 49 125% madvise_ 2 300 366 67 33 122% madvise_ 4 450 623 173 43 138% madvise_ 8 753 1110 357 45 147% madvise_ 16 1467 2127 660 41 145% madvise_ 32 2795 4109 1314 41 147%
The second test (measuring cpu cycle) syscall__ vmas cpu_5_10 c_6_8 delta_cpu per_vma % munmap__ 1 684 1790 1106 1106 262% munmap__ 2 861 2819 1958 979 327% munmap__ 4 1183 4959 3776 944 419% munmap__ 8 1999 8262 6263 783 413% munmap__ 16 3839 13099 9260 579 341% munmap__ 32 7672 23221 15549 486 303% mprotect 1 397 906 509 509 228% mprotect 2 738 3019 2281 1140 409% mprotect 4 1221 6149 4929 1232 504% mprotect 8 2356 9978 7622 953 423% mprotect 16 4961 20448 15487 968 412% mprotect 32 9882 40972 31091 972 415% madvise_ 1 351 434 82 82 123% madvise_ 2 565 752 186 93 133% madvise_ 4 872 1313 442 110 151% madvise_ 8 1508 2271 763 95 151% madvise_ 16 3078 4312 1234 77 140% madvise_ 32 5893 8376 2483 78 142%
From 5.10 to 6.8 munmap: added 250-550 ns in time, or 500-1100 in cpu cycle, per vma. mprotect: added 200-750 ns in time, or 500-1200 in cpu cycle, per vma. madvise: added 33-50 ns in time, or 70-110 in cpu cycle, per vma.
In comparison to mseal, which adds 20-40 ns or 50-100 CPU cycles, the increase from 5.10 to 6.8 is significantly larger, approximately ten times greater for munmap and mprotect.
When I discuss the mm performance with Brian Makin, an engineer worked on performance, it was brought to my attention that such a performance benchmarks, which measuring millions of mm syscall in a tight loop, may not accurately reflect real-world scenarios, such as that of a database service. Also this is tested using a single HW and ChromeOS, the data from another HW or distribution might be different. It might be best to take this data with a grain of salt.
Change history: =============== V9: - remove mmap(PROT_SEAL) and mmap(MAP_SEALABLE) (Linus, Theo de Raadt) - Update mseal_test to check for prot bit (Liam R. Howlett) - Update documentation to give more detail on sealing check (Liam R. Howlett) - Add seal_elf test. - Add performance measure data. - mseal_test: fix arm build.
V8: - perf optimization in mmap. (Liam R. Howlett) - add one testcase (test_seal_zero_address) - Update mseal.rst to add note for MAP_SEALABLE. https://lore.kernel.org/lkml/20240131175027.3287009-1-jeffxu@chromium.org/
V7: - fix index.rst (Randy Dunlap) - fix arm build (Randy Dunlap) - return EPERM for blocked operations (Theo de Raadt) https://lore.kernel.org/linux-mm/20240122152905.2220849-2-jeffxu@chromium.or...
V6: - Drop RFC from subject, Given Linus's general approval. - Adjust syscall number for mseal (main Jan.11/2024) - Code style fix (Matthew Wilcox) - selftest: use ksft macros (Muhammad Usama Anjum) - Document fix. (Randy Dunlap) https://lore.kernel.org/all/20240111234142.2944934-1-jeffxu@chromium.org/
V5: - fix build issue in mseal-Wire-up-mseal-syscall (Suggested by Linus Torvalds, and Greg KH) - updates on selftest. https://lore.kernel.org/lkml/20240109154547.1839886-1-jeffxu@chromium.org/#r
V4: (Suggested by Linus Torvalds) - new signature: mseal(start,len,flags) - 32 bit is not supported. vm_seal is removed, use vm_flags instead. - single bit in vm_flags for sealed state. - CONFIG_MSEAL kernel config is removed. - single bit of PROT_SEAL in the "Prot" field of mmap(). Other changes: - update selftest (Suggested by Muhammad Usama Anjum) - update documentation. https://lore.kernel.org/all/20240104185138.169307-1-jeffxu@chromium.org/
V3: - Abandon per-syscall approach, (Suggested by Linus Torvalds). - Organize sealing types around their functionality, such as MM_SEAL_BASE, MM_SEAL_PROT_PKEY. - Extend the scope of sealing from calls originated in userspace to both kernel and userspace. (Suggested by Linus Torvalds) - Add seal type support in mmap(). (Suggested by Pedro Falcato) - Add a new sealing type: MM_SEAL_DISCARD_RO_ANON to prevent destructive operations of madvise. (Suggested by Jann Horn and Stephen Röttger) - Make sealed VMAs mergeable. (Suggested by Jann Horn) - Add MAP_SEALABLE to mmap() - Add documentation - mseal.rst https://lore.kernel.org/linux-mm/20231212231706.2680890-2-jeffxu@chromium.or...
v2: Use _BITUL to define MM_SEAL_XX type. Use unsigned long for seal type in sys_mseal() and other functions. Remove internal VM_SEAL_XX type and convert_user_seal_type(). Remove MM_ACTION_XX type. Remove caller_origin(ON_BEHALF_OF_XX) and replace with sealing bitmask. Add more comments in code. Add a detailed commit message. https://lore.kernel.org/lkml/20231017090815.1067790-1-jeffxu@chromium.org/
v1: https://lore.kernel.org/lkml/20231016143828.647848-1-jeffxu@chromium.org/
---------------------------------------------------------------- [1] https://kernelnewbies.org/Linux_2_6_8 [2] https://v8.dev/blog/control-flow-integrity [3] https://github.com/apple-oss-distributions/xnu/blob/1031c584a5e37aff177559b9... [4] https://man.openbsd.org/mimmutable.2 [5] https://docs.google.com/document/d/1O2jwK4dxI3nRcOJuPYkonhTkNQfbmwdvxQMyXgea... [6] https://lore.kernel.org/lkml/CAG48ez3ShUYey+ZAFsU2i1RpQn0a5eOs2hzQ426FkcgnfU... [7] https://lore.kernel.org/lkml/20230515130553.2311248-1-jeffxu@chromium.org/ [8] https://github.com/peaktocreek/mmperf
Jeff Xu (5): mseal: Wire up mseal syscall mseal: add mseal syscall selftest mm/mseal memory sealing mseal:add documentation selftest mm/mseal read-only elf memory segment
Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/mseal.rst | 199 ++ arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 + arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 5 +- kernel/sys_ni.c | 1 + mm/Makefile | 4 + mm/internal.h | 37 + mm/madvise.c | 12 + mm/mmap.c | 31 +- mm/mprotect.c | 10 + mm/mremap.c | 31 + mm/mseal.c | 307 ++++ tools/testing/selftests/mm/.gitignore | 2 + tools/testing/selftests/mm/Makefile | 2 + tools/testing/selftests/mm/mseal_test.c | 1836 +++++++++++++++++++ tools/testing/selftests/mm/seal_elf.c | 183 ++ 33 files changed, 2678 insertions(+), 3 deletions(-) create mode 100644 Documentation/userspace-api/mseal.rst create mode 100644 mm/mseal.c create mode 100644 tools/testing/selftests/mm/mseal_test.c create mode 100644 tools/testing/selftests/mm/seal_elf.c
From: Jeff Xu jeffxu@chromium.org
Wire up mseal syscall for all architectures.
Signed-off-by: Jeff Xu jeffxu@chromium.org --- arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 ++ arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + include/uapi/asm-generic/unistd.h | 5 ++++- kernel/sys_ni.c | 1 + 19 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl index 8ff110826ce2..d8f96362e9f8 100644 --- a/arch/alpha/kernel/syscalls/syscall.tbl +++ b/arch/alpha/kernel/syscalls/syscall.tbl @@ -501,3 +501,4 @@ 569 common lsm_get_self_attr sys_lsm_get_self_attr 570 common lsm_set_self_attr sys_lsm_set_self_attr 571 common lsm_list_modules sys_lsm_list_modules +572 common mseal sys_mseal diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index b6c9e01e14f5..2ed7d229c8f9 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -475,3 +475,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h index 491b2b9bd553..1346579f802f 100644 --- a/arch/arm64/include/asm/unistd.h +++ b/arch/arm64/include/asm/unistd.h @@ -39,7 +39,7 @@ #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
-#define __NR_compat_syscalls 462 +#define __NR_compat_syscalls 463 #endif
#define __ARCH_WANT_SYS_CLONE diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h index 7118282d1c79..266b96acc014 100644 --- a/arch/arm64/include/asm/unistd32.h +++ b/arch/arm64/include/asm/unistd32.h @@ -929,6 +929,8 @@ __SYSCALL(__NR_lsm_get_self_attr, sys_lsm_get_self_attr) __SYSCALL(__NR_lsm_set_self_attr, sys_lsm_set_self_attr) #define __NR_lsm_list_modules 461 __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules) +#define __NR_mseal 462 +__SYSCALL(__NR_mseal, sys_mseal)
/* * Please add new compat syscalls above this comment and update diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl index 7fd43fd4c9f2..22a3cbd4c602 100644 --- a/arch/m68k/kernel/syscalls/syscall.tbl +++ b/arch/m68k/kernel/syscalls/syscall.tbl @@ -461,3 +461,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl index b00ab2cabab9..2b81a6bd78b2 100644 --- a/arch/microblaze/kernel/syscalls/syscall.tbl +++ b/arch/microblaze/kernel/syscalls/syscall.tbl @@ -467,3 +467,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl index 83cfc9eb6b88..cc869f5d5693 100644 --- a/arch/mips/kernel/syscalls/syscall_n32.tbl +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl @@ -400,3 +400,4 @@ 459 n32 lsm_get_self_attr sys_lsm_get_self_attr 460 n32 lsm_set_self_attr sys_lsm_set_self_attr 461 n32 lsm_list_modules sys_lsm_list_modules +462 n32 mseal sys_mseal diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl index 532b855df589..1464c6be6eb3 100644 --- a/arch/mips/kernel/syscalls/syscall_n64.tbl +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl @@ -376,3 +376,4 @@ 459 n64 lsm_get_self_attr sys_lsm_get_self_attr 460 n64 lsm_set_self_attr sys_lsm_set_self_attr 461 n64 lsm_list_modules sys_lsm_list_modules +462 n64 mseal sys_mseal diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl index f45c9530ea93..008ebe60263e 100644 --- a/arch/mips/kernel/syscalls/syscall_o32.tbl +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl @@ -449,3 +449,4 @@ 459 o32 lsm_get_self_attr sys_lsm_get_self_attr 460 o32 lsm_set_self_attr sys_lsm_set_self_attr 461 o32 lsm_list_modules sys_lsm_list_modules +462 o32 mseal sys_mseal diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl index b236a84c4e12..b13c21373974 100644 --- a/arch/parisc/kernel/syscalls/syscall.tbl +++ b/arch/parisc/kernel/syscalls/syscall.tbl @@ -460,3 +460,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl index 17173b82ca21..3656f1ca7a21 100644 --- a/arch/powerpc/kernel/syscalls/syscall.tbl +++ b/arch/powerpc/kernel/syscalls/syscall.tbl @@ -548,3 +548,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl index 095bb86339a7..bd0fee24ad10 100644 --- a/arch/s390/kernel/syscalls/syscall.tbl +++ b/arch/s390/kernel/syscalls/syscall.tbl @@ -464,3 +464,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal sys_mseal diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl index 86fe269f0220..bbf83a2db986 100644 --- a/arch/sh/kernel/syscalls/syscall.tbl +++ b/arch/sh/kernel/syscalls/syscall.tbl @@ -464,3 +464,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl index b23d59313589..ac6c281ccfe0 100644 --- a/arch/sparc/kernel/syscalls/syscall.tbl +++ b/arch/sparc/kernel/syscalls/syscall.tbl @@ -507,3 +507,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 5f8591ce7f25..7fd1f57ad3d3 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -466,3 +466,4 @@ 459 i386 lsm_get_self_attr sys_lsm_get_self_attr 460 i386 lsm_set_self_attr sys_lsm_set_self_attr 461 i386 lsm_list_modules sys_lsm_list_modules +462 i386 mseal sys_mseal diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 7e8d46f4147f..52df0dec70da 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -383,6 +383,7 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal
# # Due to a historical design error, certain syscalls are numbered differently diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl index dd116598fb25..67083fc1b2f5 100644 --- a/arch/xtensa/kernel/syscalls/syscall.tbl +++ b/arch/xtensa/kernel/syscalls/syscall.tbl @@ -432,3 +432,4 @@ 459 common lsm_get_self_attr sys_lsm_get_self_attr 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules +462 common mseal sys_mseal diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index 75f00965ab15..d983c48a3b6a 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -842,8 +842,11 @@ __SYSCALL(__NR_lsm_set_self_attr, sys_lsm_set_self_attr) #define __NR_lsm_list_modules 461 __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules)
+#define __NR_mseal 462 +__SYSCALL(__NR_mseal, sys_mseal) + #undef __NR_syscalls -#define __NR_syscalls 462 +#define __NR_syscalls 463
/* * 32 bit systems traditionally used different diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index faad00cce269..d7eee421d4bc 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -196,6 +196,7 @@ COND_SYSCALL(migrate_pages); COND_SYSCALL(move_pages); COND_SYSCALL(set_mempolicy_home_node); COND_SYSCALL(cachestat); +COND_SYSCALL(mseal);
COND_SYSCALL(perf_event_open); COND_SYSCALL(accept4);
From: Jeff Xu jeffxu@chromium.org
The new mseal() is an syscall on 64 bit CPU, and with following signature:
int mseal(void addr, size_t len, unsigned long flags) addr/len: memory range. flags: reserved.
mseal() blocks following operations for the given memory range.
1> Unmapping, moving to another location, and shrinking the size, via munmap() and mremap(), can leave an empty space, therefore can be replaced with a VMA with a new set of attributes.
2> Moving or expanding a different VMA into the current location, via mremap().
3> Modifying a VMA via mmap(MAP_FIXED).
4> Size expansion, via mremap(), does not appear to pose any specific risks to sealed VMAs. It is included anyway because the use case is unclear. In any case, users can rely on merging to expand a sealed VMA.
5> mprotect() and pkey_mprotect().
6> Some destructive madvice() behaviors (e.g. MADV_DONTNEED) for anonymous memory, when users don't have write permission to the memory. Those behaviors can alter region contents by discarding pages, effectively a memset(0) for anonymous memory.
Following input during RFC are incooperated into this patch:
Jann Horn: raising awareness and providing valuable insights on the destructive madvise operations. Linus Torvalds: assisting in defining system call signature and scope. Liam R. Howlett: perf optimization. Theo de Raadt: sharing the experiences and insight gained from implementing mimmutable() in OpenBSD.
Finally, the idea that inspired this patch comes from Stephen Röttger’s work in Chrome V8 CFI.
Signed-off-by: Jeff Xu jeffxu@chromium.org --- include/linux/syscalls.h | 1 + mm/Makefile | 4 + mm/internal.h | 37 +++++ mm/madvise.c | 12 ++ mm/mmap.c | 31 +++- mm/mprotect.c | 10 ++ mm/mremap.c | 31 ++++ mm/mseal.c | 307 +++++++++++++++++++++++++++++++++++++++ 8 files changed, 432 insertions(+), 1 deletion(-) create mode 100644 mm/mseal.c
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 77eb9b0e7685..abdf93951405 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -821,6 +821,7 @@ asmlinkage long sys_process_mrelease(int pidfd, unsigned int flags); asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size, unsigned long prot, unsigned long pgoff, unsigned long flags); +asmlinkage long sys_mseal(unsigned long start, size_t len, unsigned long flags); asmlinkage long sys_mbind(unsigned long start, unsigned long len, unsigned long mode, const unsigned long __user *nmask, diff --git a/mm/Makefile b/mm/Makefile index e4b5b75aaec9..cbae83f74642 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -43,6 +43,10 @@ ifdef CONFIG_CROSS_MEMORY_ATTACH mmu-$(CONFIG_MMU) += process_vm_access.o endif
+ifdef CONFIG_64BIT +mmu-$(CONFIG_MMU) += mseal.o +endif + obj-y := filemap.o mempool.o oom_kill.o fadvise.o \ maccess.o page-writeback.o folio-compat.o \ readahead.o swap.o truncate.o vmscan.o shrinker.o \ diff --git a/mm/internal.h b/mm/internal.h index f309a010d50f..ca42acee3a3f 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1221,6 +1221,43 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn, unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg, int priority);
+#ifdef CONFIG_64BIT +/* VM is sealed, in vm_flags */ +#define VM_SEALED _BITUL(63) +#endif + +#ifdef CONFIG_64BIT +static inline int can_do_mseal(unsigned long flags) +{ + if (flags) + return -EINVAL; + + return 0; +} + +bool can_modify_mm(struct mm_struct *mm, unsigned long start, + unsigned long end); +bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start, + unsigned long end, int behavior); +#else +static inline int can_do_mseal(unsigned long flags) +{ + return -EPERM; +} + +static inline bool can_modify_mm(struct mm_struct *mm, unsigned long start, + unsigned long end) +{ + return true; +} + +static inline bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start, + unsigned long end, int behavior) +{ + return true; +} +#endif + #ifdef CONFIG_SHRINKER_DEBUG static inline __printf(2, 0) int shrinker_debugfs_name_alloc( struct shrinker *shrinker, const char *fmt, va_list ap) diff --git a/mm/madvise.c b/mm/madvise.c index cfa5e7288261..8cd916a9ee1d 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1394,6 +1394,7 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start, * -EIO - an I/O error occurred while paging in data. * -EBADF - map exists, but area maps something that isn't a file. * -EAGAIN - a kernel resource was temporarily unavailable. + * -EPERM - memory is sealed. */ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int behavior) { @@ -1437,10 +1438,21 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh start = untagged_addr_remote(mm, start); end = start + len;
+ /* + * Check if the address range is sealed for do_madvise(). + * can_modify_mm_madv assumes we have acquired the lock on MM. + */ + if (!can_modify_mm_madv(mm, start, end, behavior)) { + error = -EPERM; + goto out; + } + blk_start_plug(&plug); error = madvise_walk_vmas(mm, start, end, behavior, madvise_vma_behavior); blk_finish_plug(&plug); + +out: if (write) mmap_write_unlock(mm); else diff --git a/mm/mmap.c b/mm/mmap.c index d89770eaab6b..d495fac95550 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1261,6 +1261,16 @@ unsigned long do_mmap(struct file *file, unsigned long addr, return -EEXIST; }
+ /* + * addr is returned from get_unmapped_area, + * There are two cases: + * 1> MAP_FIXED == false + * unallocated memory, no need to check sealing. + * 1> MAP_FIXED == true + * sealing is checked inside mmap_region when + * do_vmi_munmap is called. + */ + if (prot == PROT_EXEC) { pkey = execute_only_pkey(mm); if (pkey < 0) @@ -2681,6 +2691,14 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm, if (end == start) return -EINVAL;
+ /* + * Check if memory is sealed before arch_unmap. + * Prevent unmapping a sealed VMA. + * can_modify_mm assumes we have acquired the lock on MM. + */ + if (!can_modify_mm(mm, start, end)) + return -EPERM; + /* arch_unmap() might do unmaps itself. */ arch_unmap(mm, start, end);
@@ -2743,7 +2761,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr, }
/* Unmap any existing mapping in the area */ - if (do_vmi_munmap(&vmi, mm, addr, len, uf, false)) + error = do_vmi_munmap(&vmi, mm, addr, len, uf, false); + if (error == -EPERM) + return error; + else if (error) return -ENOMEM;
/* @@ -3104,6 +3125,14 @@ int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, { struct mm_struct *mm = vma->vm_mm;
+ /* + * Check if memory is sealed before arch_unmap. + * Prevent unmapping a sealed VMA. + * can_modify_mm assumes we have acquired the lock on MM. + */ + if (!can_modify_mm(mm, start, end)) + return -EPERM; + arch_unmap(mm, start, end); return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, unlock); } diff --git a/mm/mprotect.c b/mm/mprotect.c index 81991102f785..5f0f716bf4ae 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -32,6 +32,7 @@ #include <linux/sched/sysctl.h> #include <linux/userfaultfd_k.h> #include <linux/memory-tiers.h> +#include <uapi/linux/mman.h> #include <asm/cacheflush.h> #include <asm/mmu_context.h> #include <asm/tlbflush.h> @@ -743,6 +744,15 @@ static int do_mprotect_pkey(unsigned long start, size_t len, } }
+ /* + * checking if memory is sealed. + * can_modify_mm assumes we have acquired the lock on MM. + */ + if (!can_modify_mm(current->mm, start, end)) { + error = -EPERM; + goto out; + } + prev = vma_prev(&vmi); if (start > vma->vm_start) prev = vma; diff --git a/mm/mremap.c b/mm/mremap.c index 38d98465f3d8..d69b438dcf83 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -902,7 +902,25 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, if ((mm->map_count + 2) >= sysctl_max_map_count - 3) return -ENOMEM;
+ /* + * In mremap_to(). + * Move a VMA to another location, check if src addr is sealed. + * + * Place can_modify_mm here because mremap_to() + * does its own checking for address range, and we only + * check the sealing after passing those checks. + * + * can_modify_mm assumes we have acquired the lock on MM. + */ + if (!can_modify_mm(mm, addr, addr + old_len)) + return -EPERM; + if (flags & MREMAP_FIXED) { + /* + * In mremap_to(). + * VMA is moved to dst address, and munmap dst first. + * do_munmap will check if dst is sealed. + */ ret = do_munmap(mm, new_addr, new_len, uf_unmap_early); if (ret) goto out; @@ -1061,6 +1079,19 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, goto out; }
+ /* + * Below is shrink/expand case (not mremap_to()) + * Check if src address is sealed, if so, reject. + * In other words, prevent shrinking or expanding a sealed VMA. + * + * Place can_modify_mm here so we can keep the logic related to + * shrink/expand together. + */ + if (!can_modify_mm(mm, addr, addr + old_len)) { + ret = -EPERM; + goto out; + } + /* * Always allow a shrinking remap: that just unmaps * the unnecessary pages.. diff --git a/mm/mseal.c b/mm/mseal.c new file mode 100644 index 000000000000..daadac4b8125 --- /dev/null +++ b/mm/mseal.c @@ -0,0 +1,307 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Implement mseal() syscall. + * + * Copyright (c) 2023,2024 Google, Inc. + * + * Author: Jeff Xu jeffxu@chromium.org + */ + +#include <linux/mempolicy.h> +#include <linux/mman.h> +#include <linux/mm.h> +#include <linux/mm_inline.h> +#include <linux/mmu_context.h> +#include <linux/syscalls.h> +#include <linux/sched.h> +#include "internal.h" + +static inline bool vma_is_sealed(struct vm_area_struct *vma) +{ + return (vma->vm_flags & VM_SEALED); +} + +static inline void set_vma_sealed(struct vm_area_struct *vma) +{ + vm_flags_set(vma, VM_SEALED); +} + +/* + * check if a vma is sealed for modification. + * return true, if modification is allowed. + */ +static bool can_modify_vma(struct vm_area_struct *vma) +{ + if (vma_is_sealed(vma)) + return false; + + return true; +} + +static bool is_madv_discard(int behavior) +{ + return behavior & + (MADV_FREE | MADV_DONTNEED | MADV_DONTNEED_LOCKED | + MADV_REMOVE | MADV_DONTFORK | MADV_WIPEONFORK); +} + +static bool is_ro_anon(struct vm_area_struct *vma) +{ + /* check anonymous mapping. */ + if (vma->vm_file || vma->vm_flags & VM_SHARED) + return false; + + /* + * check for non-writable: + * PROT=RO or PKRU is not writeable. + */ + if (!(vma->vm_flags & VM_WRITE) || + !arch_vma_access_permitted(vma, true, false, false)) + return true; + + return false; +} + +/* + * Check if the vmas of a memory range are allowed to be modified. + * the memory ranger can have a gap (unallocated memory). + * return true, if it is allowed. + */ +bool can_modify_mm(struct mm_struct *mm, unsigned long start, unsigned long end) +{ + struct vm_area_struct *vma; + + VMA_ITERATOR(vmi, mm, start); + + /* going through each vma to check. */ + for_each_vma_range(vmi, vma, end) { + if (!can_modify_vma(vma)) + return false; + } + + /* Allow by default. */ + return true; +} + +/* + * Check if the vmas of a memory range are allowed to be modified by madvise. + * the memory ranger can have a gap (unallocated memory). + * return true, if it is allowed. + */ +bool can_modify_mm_madv(struct mm_struct *mm, unsigned long start, unsigned long end, + int behavior) +{ + struct vm_area_struct *vma; + + VMA_ITERATOR(vmi, mm, start); + + if (!is_madv_discard(behavior)) + return true; + + /* going through each vma to check. */ + for_each_vma_range(vmi, vma, end) + if (is_ro_anon(vma) && !can_modify_vma(vma)) + return false; + + /* Allow by default. */ + return true; +} + +static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma, + struct vm_area_struct **prev, unsigned long start, + unsigned long end, vm_flags_t newflags) +{ + int ret = 0; + vm_flags_t oldflags = vma->vm_flags; + + if (newflags == oldflags) + goto out; + + vma = vma_modify_flags(vmi, *prev, vma, start, end, newflags); + if (IS_ERR(vma)) { + ret = PTR_ERR(vma); + goto out; + } + + set_vma_sealed(vma); +out: + *prev = vma; + return ret; +} + +/* + * Check for do_mseal: + * 1> start is part of a valid vma. + * 2> end is part of a valid vma. + * 3> No gap (unallocated address) between start and end. + * 4> map is sealable. + */ +static int check_mm_seal(unsigned long start, unsigned long end) +{ + struct vm_area_struct *vma; + unsigned long nstart = start; + + VMA_ITERATOR(vmi, current->mm, start); + + /* going through each vma to check. */ + for_each_vma_range(vmi, vma, end) { + if (vma->vm_start > nstart) + /* unallocated memory found. */ + return -ENOMEM; + + if (vma->vm_end >= end) + return 0; + + nstart = vma->vm_end; + } + + return -ENOMEM; +} + +/* + * Apply sealing. + */ +static int apply_mm_seal(unsigned long start, unsigned long end) +{ + unsigned long nstart; + struct vm_area_struct *vma, *prev; + + VMA_ITERATOR(vmi, current->mm, start); + + vma = vma_iter_load(&vmi); + /* + * Note: check_mm_seal should already checked ENOMEM case. + * so vma should not be null, same for the other ENOMEM cases. + */ + prev = vma_prev(&vmi); + if (start > vma->vm_start) + prev = vma; + + nstart = start; + for_each_vma_range(vmi, vma, end) { + int error; + unsigned long tmp; + vm_flags_t newflags; + + newflags = vma->vm_flags | VM_SEALED; + tmp = vma->vm_end; + if (tmp > end) + tmp = end; + error = mseal_fixup(&vmi, vma, &prev, nstart, tmp, newflags); + if (error) + return error; + nstart = vma_iter_end(&vmi); + } + + return 0; +} + +/* + * mseal(2) seals the VM's meta data from + * selected syscalls. + * + * addr/len: VM address range. + * + * The address range by addr/len must meet: + * start (addr) must be in a valid VMA. + * end (addr + len) must be in a valid VMA. + * no gap (unallocated memory) between start and end. + * start (addr) must be page aligned. + * + * len: len will be page aligned implicitly. + * + * Below VMA operations are blocked after sealing. + * 1> Unmapping, moving to another location, and shrinking + * the size, via munmap() and mremap(), can leave an empty + * space, therefore can be replaced with a VMA with a new + * set of attributes. + * 2> Moving or expanding a different vma into the current location, + * via mremap(). + * 3> Modifying a VMA via mmap(MAP_FIXED). + * 4> Size expansion, via mremap(), does not appear to pose any + * specific risks to sealed VMAs. It is included anyway because + * the use case is unclear. In any case, users can rely on + * merging to expand a sealed VMA. + * 5> mprotect and pkey_mprotect. + * 6> Some destructive madvice() behavior (e.g. MADV_DONTNEED) + * for anonymous memory, when users don't have write permission to the + * memory. Those behaviors can alter region contents by discarding pages, + * effectively a memset(0) for anonymous memory. + * + * flags: reserved. + * + * return values: + * zero: success. + * -EINVAL: + * invalid input flags. + * start address is not page aligned. + * Address arange (start + len) overflow. + * -ENOMEM: + * addr is not a valid address (not allocated). + * end (start + len) is not a valid address. + * a gap (unallocated memory) between start and end. + * -EPERM: + * - In 32 bit architecture, sealing is not supported. + * Note: + * user can call mseal(2) multiple times, adding a seal on an + * already sealed memory is a no-action (no error). + * + * unseal() is not supported. + */ +static int do_mseal(unsigned long start, size_t len_in, unsigned long flags) +{ + size_t len; + int ret = 0; + unsigned long end; + struct mm_struct *mm = current->mm; + + ret = can_do_mseal(flags); + if (ret) + return ret; + + start = untagged_addr(start); + if (!PAGE_ALIGNED(start)) + return -EINVAL; + + len = PAGE_ALIGN(len_in); + /* Check to see whether len was rounded up from small -ve to zero. */ + if (len_in && !len) + return -EINVAL; + + end = start + len; + if (end < start) + return -EINVAL; + + if (end == start) + return 0; + + if (mmap_write_lock_killable(mm)) + return -EINTR; + + /* + * First pass, this helps to avoid + * partial sealing in case of error in input address range, + * e.g. ENOMEM error. + */ + ret = check_mm_seal(start, end); + if (ret) + goto out; + + /* + * Second pass, this should success, unless there are errors + * from vma_modify_flags, e.g. merge/split error, or process + * reaching the max supported VMAs, however, those cases shall + * be rare. + */ + ret = apply_mm_seal(start, end); + +out: + mmap_write_unlock(current->mm); + return ret; +} + +SYSCALL_DEFINE3(mseal, unsigned long, start, size_t, len, unsigned long, + flags) +{ + return do_mseal(start, len, flags); +}
From: Jeff Xu jeffxu@chromium.org
selftest for memory sealing change in mmap() and mseal().
Signed-off-by: Jeff Xu jeffxu@chromium.org --- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + tools/testing/selftests/mm/mseal_test.c | 1836 +++++++++++++++++++++++ 3 files changed, 1838 insertions(+) create mode 100644 tools/testing/selftests/mm/mseal_test.c
diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index 4ff10ea61461..76474c51c786 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -46,3 +46,4 @@ gup_longterm mkdirty va_high_addr_switch hugetlb_fault_after_madv +mseal_test diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index 2453add65d12..ba36a5c2b1fc 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -59,6 +59,7 @@ TEST_GEN_FILES += mlock2-tests TEST_GEN_FILES += mrelease_test TEST_GEN_FILES += mremap_dontunmap TEST_GEN_FILES += mremap_test +TEST_GEN_FILES += mseal_test TEST_GEN_FILES += on-fault-limit TEST_GEN_FILES += pagemap_ioctl TEST_GEN_FILES += thuge-gen diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c new file mode 100644 index 000000000000..06c780d1d8e5 --- /dev/null +++ b/tools/testing/selftests/mm/mseal_test.c @@ -0,0 +1,1836 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <sys/mman.h> +#include <stdint.h> +#include <unistd.h> +#include <string.h> +#include <sys/time.h> +#include <sys/resource.h> +#include <stdbool.h> +#include "../kselftest.h" +#include <syscall.h> +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> +#include <assert.h> +#include <fcntl.h> +#include <assert.h> +#include <sys/ioctl.h> +#include <sys/vfs.h> +#include <sys/stat.h> + +/* + * need those definition for manually build using gcc. + * gcc -I ../../../../usr/include -DDEBUG -O3 -DDEBUG -O3 mseal_test.c -o mseal_test + */ +#ifndef PKEY_DISABLE_ACCESS +# define PKEY_DISABLE_ACCESS 0x1 +#endif + +#ifndef PKEY_DISABLE_WRITE +# define PKEY_DISABLE_WRITE 0x2 +#endif + +#ifndef PKEY_BITS_PER_KEY +#define PKEY_BITS_PER_PKEY 2 +#endif + +#ifndef PKEY_MASK +#define PKEY_MASK (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE) +#endif + +#define FAIL_TEST_IF_FALSE(c) do {\ + if (!(c)) {\ + ksft_test_result_fail("%s, line:%d\n", __func__, __LINE__);\ + goto test_end;\ + } \ + } \ + while (0) + +#define SKIP_TEST_IF_FALSE(c) do {\ + if (!(c)) {\ + ksft_test_result_skip("%s, line:%d\n", __func__, __LINE__);\ + goto test_end;\ + } \ + } \ + while (0) + + +#define TEST_END_CHECK() {\ + ksft_test_result_pass("%s\n", __func__);\ + return;\ +test_end:\ + return;\ +} + +#ifndef u64 +#define u64 unsigned long long +#endif + +static unsigned long get_vma_size(void *addr, int *prot) +{ + FILE *maps; + char line[256]; + int size = 0; + uintptr_t addr_start, addr_end; + char protstr[5]; + *prot = 0; + + maps = fopen("/proc/self/maps", "r"); + if (!maps) + return 0; + + while (fgets(line, sizeof(line), maps)) { + if (sscanf(line, "%lx-%lx %4s", &addr_start, &addr_end, &protstr) == 3) { + if (addr_start == (uintptr_t) addr) { + size = addr_end - addr_start; + if (protstr[0] == 'r') + *prot |= 0x4; + if (protstr[1] == 'w') + *prot |= 0x2; + if (protstr[2] == 'x') + *prot |= 0x1; + break; + } + } + } + fclose(maps); + return size; +} + +/* + * define sys_xyx to call syscall directly. + */ +static int sys_mseal(void *start, size_t len) +{ + int sret; + + errno = 0; + sret = syscall(__NR_mseal, start, len, 0); + return sret; +} + +static int sys_mprotect(void *ptr, size_t size, unsigned long prot) +{ + int sret; + + errno = 0; + sret = syscall(__NR_mprotect, ptr, size, prot); + return sret; +} + +static int sys_mprotect_pkey(void *ptr, size_t size, unsigned long orig_prot, + unsigned long pkey) +{ + int sret; + + errno = 0; + sret = syscall(__NR_pkey_mprotect, ptr, size, orig_prot, pkey); + return sret; +} + +static void *sys_mmap(void *addr, unsigned long len, unsigned long prot, + unsigned long flags, unsigned long fd, unsigned long offset) +{ + void *sret; + + errno = 0; + sret = (void *) syscall(__NR_mmap, addr, len, prot, + flags, fd, offset); + return sret; +} + +static int sys_munmap(void *ptr, size_t size) +{ + int sret; + + errno = 0; + sret = syscall(__NR_munmap, ptr, size); + return sret; +} + +static int sys_madvise(void *start, size_t len, int types) +{ + int sret; + + errno = 0; + sret = syscall(__NR_madvise, start, len, types); + return sret; +} + +static int sys_pkey_alloc(unsigned long flags, unsigned long init_val) +{ + int ret = syscall(__NR_pkey_alloc, flags, init_val); + + return ret; +} + +static unsigned int __read_pkey_reg(void) +{ + unsigned int pkey_reg = 0; +#if defined(__i386__) || defined(__x86_64__) /* arch */ + unsigned int eax, edx; + unsigned int ecx = 0; + + asm volatile(".byte 0x0f,0x01,0xee\n\t" + : "=a" (eax), "=d" (edx) + : "c" (ecx)); + pkey_reg = eax; +#endif + return pkey_reg; +} + +static void __write_pkey_reg(u64 pkey_reg) +{ +#if defined(__i386__) || defined(__x86_64__) /* arch */ + unsigned int eax = pkey_reg; + unsigned int ecx = 0; + unsigned int edx = 0; + + asm volatile(".byte 0x0f,0x01,0xef\n\t" + : : "a" (eax), "c" (ecx), "d" (edx)); + assert(pkey_reg == __read_pkey_reg()); +#endif +} + +static unsigned long pkey_bit_position(int pkey) +{ + return pkey * PKEY_BITS_PER_PKEY; +} + +static u64 set_pkey_bits(u64 reg, int pkey, u64 flags) +{ + unsigned long shift = pkey_bit_position(pkey); + + /* mask out bits from pkey in old value */ + reg &= ~((u64)PKEY_MASK << shift); + /* OR in new bits for pkey */ + reg |= (flags & PKEY_MASK) << shift; + return reg; +} + +static void set_pkey(int pkey, unsigned long pkey_value) +{ + unsigned long mask = (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE); + u64 new_pkey_reg; + + assert(!(pkey_value & ~mask)); + new_pkey_reg = set_pkey_bits(__read_pkey_reg(), pkey, pkey_value); + __write_pkey_reg(new_pkey_reg); +} + +static void setup_single_address(int size, void **ptrOut) +{ + void *ptr; + + ptr = sys_mmap(NULL, size, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + assert(ptr != (void *)-1); + *ptrOut = ptr; +} + +static void setup_single_address_rw(int size, void **ptrOut) +{ + void *ptr; + unsigned long mapflags = MAP_ANONYMOUS | MAP_PRIVATE; + + ptr = sys_mmap(NULL, size, PROT_READ | PROT_WRITE, mapflags, -1, 0); + assert(ptr != (void *)-1); + *ptrOut = ptr; +} + +static void clean_single_address(void *ptr, int size) +{ + int ret; + + ret = munmap(ptr, size); + assert(!ret); +} + +static void seal_single_address(void *ptr, int size) +{ + int ret; + + ret = sys_mseal(ptr, size); + assert(!ret); +} + +bool seal_support(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + + ptr = sys_mmap(NULL, page_size, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (ptr == (void *) -1) + return false; + + ret = sys_mseal(ptr, page_size); + if (ret < 0) + return false; + + return true; +} + +bool pkey_supported(void) +{ +#if defined(__i386__) || defined(__x86_64__) /* arch */ + int pkey = sys_pkey_alloc(0, 0); + + if (pkey > 0) + return true; +#endif + return false; +} + +static void test_seal_addseal(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_unmapped_start(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* munmap 2 pages from ptr. */ + ret = sys_munmap(ptr, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* mprotect will fail because 2 pages from ptr are unmapped. */ + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(ret < 0); + + /* mseal will fail because 2 pages from ptr are unmapped. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(ret < 0); + + ret = sys_mseal(ptr + 2 * page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_unmapped_middle(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* munmap 2 pages from ptr + page. */ + ret = sys_munmap(ptr + page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* mprotect will fail, since middle 2 pages are unmapped. */ + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(ret < 0); + + /* mseal will fail as well. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* we still can add seal to the first page and last page*/ + ret = sys_mseal(ptr, page_size); + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_mseal(ptr + 3 * page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_unmapped_end(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* unmap last 2 pages. */ + ret = sys_munmap(ptr + 2 * page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* mprotect will fail since last 2 pages are unmapped. */ + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(ret < 0); + + /* mseal will fail as well. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* The first 2 pages is not sealed, and can add seals */ + ret = sys_mseal(ptr, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_multiple_vmas(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* use mprotect to split the vma into 3. */ + ret = sys_mprotect(ptr + page_size, 2 * page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* mprotect will get applied to all 4 pages - 3 VMAs. */ + ret = sys_mprotect(ptr, size, PROT_READ); + FAIL_TEST_IF_FALSE(!ret); + + /* use mprotect to split the vma into 3. */ + ret = sys_mprotect(ptr + page_size, 2 * page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* mseal get applied to all 4 pages - 3 VMAs. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_split_start(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* use mprotect to split at middle */ + ret = sys_mprotect(ptr, 2 * page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* seal the first page, this will split the VMA */ + ret = sys_mseal(ptr, page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* add seal to the remain 3 pages */ + ret = sys_mseal(ptr + page_size, 3 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_split_end(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + /* use mprotect to split at middle */ + ret = sys_mprotect(ptr, 2 * page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* seal the last page */ + ret = sys_mseal(ptr + 3 * page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* Adding seals to the first 3 pages */ + ret = sys_mseal(ptr, 3 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_invalid_input(void) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(8 * page_size, &ptr); + clean_single_address(ptr + 4 * page_size, 4 * page_size); + + /* invalid flag */ + ret = syscall(__NR_mseal, ptr, size, 0x20); + FAIL_TEST_IF_FALSE(ret < 0); + + /* unaligned address */ + ret = sys_mseal(ptr + 1, 2 * page_size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* length too big */ + ret = sys_mseal(ptr, 5 * page_size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* length overflow */ + ret = sys_mseal(ptr, UINT64_MAX/page_size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* start is not in a valid VMA */ + ret = sys_mseal(ptr - page_size, 5 * page_size); + FAIL_TEST_IF_FALSE(ret < 0); + + TEST_END_CHECK(); +} + +static void test_seal_zero_length(void) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + ret = sys_mprotect(ptr, 0, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* seal 0 length will be OK, same as mprotect */ + ret = sys_mseal(ptr, 0); + FAIL_TEST_IF_FALSE(!ret); + + /* verify the 4 pages are not sealed by previous call. */ + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_zero_address(void) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + int prot; + + /* use mmap to change protection. */ + ptr = sys_mmap(0, size, PROT_NONE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + FAIL_TEST_IF_FALSE(ptr == 0); + + size = get_vma_size(ptr, &prot); + FAIL_TEST_IF_FALSE(size == 4 * page_size); + + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + /* verify the 4 pages are sealed by previous call. */ + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(ret); + + TEST_END_CHECK(); +} + +static void test_seal_twice(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + + setup_single_address(size, &ptr); + + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + /* apply the same seal will be OK. idempotent. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) + seal_single_address(ptr, size); + + ret = sys_mprotect(ptr, size, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_start_mprotect(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) + seal_single_address(ptr, page_size); + + /* the first page is sealed. */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + /* pages after the first page is not sealed. */ + ret = sys_mprotect(ptr + page_size, page_size * 3, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_end_mprotect(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) + seal_single_address(ptr + page_size, 3 * page_size); + + /* first page is not sealed */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* last 3 page are sealed */ + ret = sys_mprotect(ptr + page_size, page_size * 3, + PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_unalign_len(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) + seal_single_address(ptr, page_size * 2 - 1); + + /* 2 pages are sealed. */ + ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_mprotect(ptr + page_size * 2, page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_unalign_len_variant_2(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + if (seal) + seal_single_address(ptr, page_size * 2 + 1); + + /* 3 pages are sealed. */ + ret = sys_mprotect(ptr, page_size * 3, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_mprotect(ptr + page_size * 3, page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_two_vma(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split */ + ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) + seal_single_address(ptr, page_size * 4); + + ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_mprotect(ptr + page_size * 2, page_size * 2, + PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_two_vma_with_split(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split as two vma. */ + ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* mseal can apply across 2 vma, also split them. */ + if (seal) + seal_single_address(ptr + page_size, page_size * 2); + + /* the first page is not sealed. */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* the second page is sealed. */ + ret = sys_mprotect(ptr + page_size, page_size, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + /* the third page is sealed. */ + ret = sys_mprotect(ptr + 2 * page_size, page_size, + PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + /* the fouth page is not sealed. */ + ret = sys_mprotect(ptr + 3 * page_size, page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_partial_mprotect(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* seal one page. */ + if (seal) + seal_single_address(ptr, page_size); + + /* mprotect first 2 page will fail, since the first page are sealed. */ + ret = sys_mprotect(ptr, 2 * page_size, PROT_READ | PROT_WRITE); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_two_vma_with_gap(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split. */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* use mprotect to split. */ + ret = sys_mprotect(ptr + 3 * page_size, page_size, + PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* use munmap to free two pages in the middle */ + ret = sys_munmap(ptr + page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* mprotect will fail, because there is a gap in the address. */ + /* notes, internally mprotect still updated the first page. */ + ret = sys_mprotect(ptr, 4 * page_size, PROT_READ); + FAIL_TEST_IF_FALSE(ret < 0); + + /* mseal will fail as well. */ + ret = sys_mseal(ptr, 4 * page_size); + FAIL_TEST_IF_FALSE(ret < 0); + + /* the first page is not sealed. */ + ret = sys_mprotect(ptr, page_size, PROT_READ); + FAIL_TEST_IF_FALSE(ret == 0); + + /* the last page is not sealed. */ + ret = sys_mprotect(ptr + 3 * page_size, page_size, PROT_READ); + FAIL_TEST_IF_FALSE(ret == 0); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_split(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split. */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* seal all 4 pages. */ + if (seal) { + ret = sys_mseal(ptr, 4 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* mprotect is sealed. */ + ret = sys_mprotect(ptr, 2 * page_size, PROT_READ); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + + ret = sys_mprotect(ptr + 2 * page_size, 2 * page_size, PROT_READ); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_mprotect_merge(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split one page. */ + ret = sys_mprotect(ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + /* seal first two pages. */ + if (seal) { + ret = sys_mseal(ptr, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* 2 pages are sealed. */ + ret = sys_mprotect(ptr, 2 * page_size, PROT_READ); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + /* last 2 pages are not sealed. */ + ret = sys_mprotect(ptr + 2 * page_size, 2 * page_size, PROT_READ); + FAIL_TEST_IF_FALSE(ret == 0); + + TEST_END_CHECK(); +} + +static void test_seal_munmap(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* 4 pages are sealed. */ + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +/* + * allocate 4 pages, + * use mprotect to split it as two VMAs + * seal the whole range + * munmap will fail on both + */ +static void test_seal_munmap_two_vma(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + /* use mprotect to split */ + ret = sys_mprotect(ptr, page_size * 2, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + ret = sys_munmap(ptr, page_size * 2); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr + page_size, page_size * 2); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +/* + * allocate a VMA with 4 pages. + * munmap the middle 2 pages. + * seal the whole 4 pages, will fail. + * munmap the first page will be OK. + * munmap the last page will be OK. + */ +static void test_seal_munmap_vma_with_gap(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + ret = sys_munmap(ptr + page_size, page_size * 2); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) { + /* can't have gap in the middle. */ + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(ret < 0); + } + + ret = sys_munmap(ptr, page_size); + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr + page_size * 2, page_size); + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_munmap_start_freed(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + int prot; + + setup_single_address(size, &ptr); + + /* unmap the first page. */ + ret = sys_munmap(ptr, page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* seal the last 3 pages. */ + if (seal) { + ret = sys_mseal(ptr + page_size, 3 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* unmap from the first page. */ + ret = sys_munmap(ptr, size); + if (seal) { + FAIL_TEST_IF_FALSE(ret < 0); + + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == page_size * 3); + } else { + /* note: this will be OK, even the first page is */ + /* already unmapped. */ + FAIL_TEST_IF_FALSE(!ret); + + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == 0); + } + + TEST_END_CHECK(); +} + +static void test_munmap_end_freed(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + /* unmap last page. */ + ret = sys_munmap(ptr + page_size * 3, page_size); + FAIL_TEST_IF_FALSE(!ret); + + /* seal the first 3 pages. */ + if (seal) { + ret = sys_mseal(ptr, 3 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* unmap all pages. */ + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_munmap_middle_freed(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + int prot; + + setup_single_address(size, &ptr); + /* unmap 2 pages in the middle. */ + ret = sys_munmap(ptr + page_size, page_size * 2); + FAIL_TEST_IF_FALSE(!ret); + + /* seal the first page. */ + if (seal) { + ret = sys_mseal(ptr, page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* munmap all 4 pages. */ + ret = sys_munmap(ptr, size); + if (seal) { + FAIL_TEST_IF_FALSE(ret < 0); + + size = get_vma_size(ptr, &prot); + FAIL_TEST_IF_FALSE(size == page_size); + + size = get_vma_size(ptr + page_size * 3, &prot); + FAIL_TEST_IF_FALSE(size == page_size); + } else { + FAIL_TEST_IF_FALSE(!ret); + + size = get_vma_size(ptr, &prot); + FAIL_TEST_IF_FALSE(size == 0); + + size = get_vma_size(ptr + page_size * 3, &prot); + FAIL_TEST_IF_FALSE(size == 0); + } + + TEST_END_CHECK(); +} + +static void test_seal_mremap_shrink(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* shrink from 4 pages to 2 pages. */ + ret2 = mremap(ptr, size, 2 * page_size, 0, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 != MAP_FAILED); + + } + + TEST_END_CHECK(); +} + +static void test_seal_mremap_expand(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + /* ummap last 2 pages. */ + ret = sys_munmap(ptr + 2 * page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) { + ret = sys_mseal(ptr, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* expand from 2 page to 4 pages. */ + ret2 = mremap(ptr, 2 * page_size, 4 * page_size, 0, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 == ptr); + + } + + TEST_END_CHECK(); +} + +static void test_seal_mremap_move(bool seal) +{ + void *ptr, *newPtr; + unsigned long page_size = getpagesize(); + unsigned long size = page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + setup_single_address(size, &newPtr); + clean_single_address(newPtr, size); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* move from ptr to fixed address. */ + ret2 = mremap(ptr, size, size, MREMAP_MAYMOVE | MREMAP_FIXED, newPtr); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 != MAP_FAILED); + + } + + TEST_END_CHECK(); +} + +static void test_seal_mmap_overwrite_prot(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* use mmap to change protection. */ + ret2 = sys_mmap(ptr, size, PROT_NONE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == ptr); + + TEST_END_CHECK(); +} + +static void test_seal_mmap_expand(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 12 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + /* ummap last 4 pages. */ + ret = sys_munmap(ptr + 8 * page_size, 4 * page_size); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) { + ret = sys_mseal(ptr, 8 * page_size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* use mmap to expand. */ + ret2 = sys_mmap(ptr, size, PROT_READ, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == ptr); + + TEST_END_CHECK(); +} + +static void test_seal_mmap_shrink(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 12 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* use mmap to shrink. */ + ret2 = sys_mmap(ptr, 8 * page_size, PROT_READ, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == ptr); + + TEST_END_CHECK(); +} + +static void test_seal_mremap_shrink_fixed(bool seal) +{ + void *ptr; + void *newAddr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + setup_single_address(size, &newAddr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* mremap to move and shrink to fixed address */ + ret2 = mremap(ptr, size, 2 * page_size, MREMAP_MAYMOVE | MREMAP_FIXED, + newAddr); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == newAddr); + + TEST_END_CHECK(); +} + +static void test_seal_mremap_expand_fixed(bool seal) +{ + void *ptr; + void *newAddr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(page_size, &ptr); + setup_single_address(size, &newAddr); + + if (seal) { + ret = sys_mseal(newAddr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* mremap to move and expand to fixed address */ + ret2 = mremap(ptr, page_size, size, MREMAP_MAYMOVE | MREMAP_FIXED, + newAddr); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == newAddr); + + TEST_END_CHECK(); +} + +static void test_seal_mremap_move_fixed(bool seal) +{ + void *ptr; + void *newAddr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + setup_single_address(size, &newAddr); + + if (seal) { + ret = sys_mseal(newAddr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* mremap to move to fixed address */ + ret2 = mremap(ptr, size, size, MREMAP_MAYMOVE | MREMAP_FIXED, newAddr); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else + FAIL_TEST_IF_FALSE(ret2 == newAddr); + + TEST_END_CHECK(); +} + +static void test_seal_mremap_move_fixed_zero(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* + * MREMAP_FIXED can move the mapping to zero address + */ + ret2 = mremap(ptr, size, 2 * page_size, MREMAP_MAYMOVE | MREMAP_FIXED, + 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 == 0); + + } + + TEST_END_CHECK(); +} + +static void test_seal_mremap_move_dontunmap(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* mremap to move, and don't unmap src addr. */ + ret2 = mremap(ptr, size, size, MREMAP_MAYMOVE | MREMAP_DONTUNMAP, 0); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 != MAP_FAILED); + + } + + TEST_END_CHECK(); +} + +static void test_seal_mremap_move_dontunmap_anyaddr(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + void *ret2; + + setup_single_address(size, &ptr); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* + * The 0xdeaddead should not have effect on dest addr + * when MREMAP_DONTUNMAP is set. + */ + ret2 = mremap(ptr, size, size, MREMAP_MAYMOVE | MREMAP_DONTUNMAP, + 0xdeaddead); + if (seal) { + FAIL_TEST_IF_FALSE(ret2 == MAP_FAILED); + FAIL_TEST_IF_FALSE(errno == EPERM); + } else { + FAIL_TEST_IF_FALSE(ret2 != MAP_FAILED); + FAIL_TEST_IF_FALSE((long)ret2 != 0xdeaddead); + + } + + TEST_END_CHECK(); +} + + +static void test_seal_merge_and_split(void) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size; + int ret; + int prot; + + /* (24 RO) */ + setup_single_address(24 * page_size, &ptr); + + /* use mprotect(NONE) to set out boundary */ + /* (1 NONE) (22 RO) (1 NONE) */ + ret = sys_mprotect(ptr, page_size, PROT_NONE); + FAIL_TEST_IF_FALSE(!ret); + ret = sys_mprotect(ptr + 23 * page_size, page_size, PROT_NONE); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == 22 * page_size); + FAIL_TEST_IF_FALSE(prot == 4); + + /* use mseal to split from beginning */ + /* (1 NONE) (1 RO_SEAL) (21 RO) (1 NONE) */ + ret = sys_mseal(ptr + page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + size = get_vma_size(ptr + 2 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == 21 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + /* use mseal to split from the end. */ + /* (1 NONE) (1 RO_SEAL) (20 RO) (1 RO_SEAL) (1 NONE) */ + ret = sys_mseal(ptr + 22 * page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + 22 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + size = get_vma_size(ptr + 2 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == 20 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + /* merge with prev. */ + /* (1 NONE) (2 RO_SEAL) (19 RO) (1 RO_SEAL) (1 NONE) */ + ret = sys_mseal(ptr + 2 * page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == 2 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + /* merge with after. */ + /* (1 NONE) (2 RO_SEAL) (18 RO) (2 RO_SEALS) (1 NONE) */ + ret = sys_mseal(ptr + 21 * page_size, page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + 21 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == 2 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + /* split and merge from prev */ + /* (1 NONE) (3 RO_SEAL) (17 RO) (2 RO_SEALS) (1 NONE) */ + ret = sys_mseal(ptr + 2 * page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + 1 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == 3 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + ret = sys_munmap(ptr + page_size, page_size); + FAIL_TEST_IF_FALSE(ret < 0); + ret = sys_mprotect(ptr + 2 * page_size, page_size, PROT_NONE); + FAIL_TEST_IF_FALSE(ret < 0); + + /* split and merge from next */ + /* (1 NONE) (3 RO_SEAL) (16 RO) (3 RO_SEALS) (1 NONE) */ + ret = sys_mseal(ptr + 20 * page_size, 2 * page_size); + FAIL_TEST_IF_FALSE(!ret); + FAIL_TEST_IF_FALSE(prot == 0x4); + size = get_vma_size(ptr + 20 * page_size, &prot); + FAIL_TEST_IF_FALSE(size == 3 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + /* merge from middle of prev and middle of next. */ + /* (1 NONE) (22 RO_SEAL) (1 NONE) */ + ret = sys_mseal(ptr + 2 * page_size, 20 * page_size); + FAIL_TEST_IF_FALSE(!ret); + size = get_vma_size(ptr + page_size, &prot); + FAIL_TEST_IF_FALSE(size == 22 * page_size); + FAIL_TEST_IF_FALSE(prot == 0x4); + + TEST_END_CHECK(); +} + +static void test_seal_discard_ro_anon_on_rw(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address_rw(size, &ptr); + FAIL_TEST_IF_FALSE(ptr != (void *)-1); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* sealing doesn't take effect on RW memory. */ + ret = sys_madvise(ptr, size, MADV_DONTNEED); + FAIL_TEST_IF_FALSE(!ret); + + /* base seal still apply. */ + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_discard_ro_anon_on_pkey(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + int pkey; + + SKIP_TEST_IF_FALSE(pkey_supported()); + + setup_single_address_rw(size, &ptr); + FAIL_TEST_IF_FALSE(ptr != (void *)-1); + + pkey = sys_pkey_alloc(0, 0); + FAIL_TEST_IF_FALSE(pkey > 0); + + ret = sys_mprotect_pkey((void *)ptr, size, PROT_READ | PROT_WRITE, pkey); + FAIL_TEST_IF_FALSE(!ret); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* sealing doesn't take effect if PKRU allow write. */ + set_pkey(pkey, 0); + ret = sys_madvise(ptr, size, MADV_DONTNEED); + FAIL_TEST_IF_FALSE(!ret); + + /* sealing will take effect if PKRU deny write. */ + set_pkey(pkey, PKEY_DISABLE_WRITE); + ret = sys_madvise(ptr, size, MADV_DONTNEED); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + /* base seal still apply. */ + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_discard_ro_anon_on_filebacked(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + int fd; + unsigned long mapflags = MAP_PRIVATE; + + fd = memfd_create("test", 0); + FAIL_TEST_IF_FALSE(fd > 0); + + ret = fallocate(fd, 0, 0, size); + FAIL_TEST_IF_FALSE(!ret); + + ptr = sys_mmap(NULL, size, PROT_READ, mapflags, fd, 0); + FAIL_TEST_IF_FALSE(ptr != MAP_FAILED); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* sealing doesn't apply for file backed mapping. */ + ret = sys_madvise(ptr, size, MADV_DONTNEED); + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + close(fd); + + TEST_END_CHECK(); +} + +static void test_seal_discard_ro_anon_on_shared(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + unsigned long mapflags = MAP_ANONYMOUS | MAP_SHARED; + + ptr = sys_mmap(NULL, size, PROT_READ, mapflags, -1, 0); + FAIL_TEST_IF_FALSE(ptr != (void *)-1); + + if (seal) { + ret = sys_mseal(ptr, size); + FAIL_TEST_IF_FALSE(!ret); + } + + /* sealing doesn't apply for shared mapping. */ + ret = sys_madvise(ptr, size, MADV_DONTNEED); + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +static void test_seal_discard_ro_anon(bool seal) +{ + void *ptr; + unsigned long page_size = getpagesize(); + unsigned long size = 4 * page_size; + int ret; + + setup_single_address(size, &ptr); + + if (seal) + seal_single_address(ptr, size); + + ret = sys_madvise(ptr, size, MADV_DONTNEED); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + ret = sys_munmap(ptr, size); + if (seal) + FAIL_TEST_IF_FALSE(ret < 0); + else + FAIL_TEST_IF_FALSE(!ret); + + TEST_END_CHECK(); +} + +int main(int argc, char **argv) +{ + bool test_seal = seal_support(); + + ksft_print_header(); + + if (!test_seal) + ksft_exit_skip("sealing not supported, check CONFIG_64BIT\n"); + + if (!pkey_supported()) + ksft_print_msg("PKEY not supported\n"); + + ksft_set_plan(80); + + test_seal_addseal(); + test_seal_unmapped_start(); + test_seal_unmapped_middle(); + test_seal_unmapped_end(); + test_seal_multiple_vmas(); + test_seal_split_start(); + test_seal_split_end(); + test_seal_invalid_input(); + test_seal_zero_length(); + test_seal_twice(); + + test_seal_mprotect(false); + test_seal_mprotect(true); + + test_seal_start_mprotect(false); + test_seal_start_mprotect(true); + + test_seal_end_mprotect(false); + test_seal_end_mprotect(true); + + test_seal_mprotect_unalign_len(false); + test_seal_mprotect_unalign_len(true); + + test_seal_mprotect_unalign_len_variant_2(false); + test_seal_mprotect_unalign_len_variant_2(true); + + test_seal_mprotect_two_vma(false); + test_seal_mprotect_two_vma(true); + + test_seal_mprotect_two_vma_with_split(false); + test_seal_mprotect_two_vma_with_split(true); + + test_seal_mprotect_partial_mprotect(false); + test_seal_mprotect_partial_mprotect(true); + + test_seal_mprotect_two_vma_with_gap(false); + test_seal_mprotect_two_vma_with_gap(true); + + test_seal_mprotect_merge(false); + test_seal_mprotect_merge(true); + + test_seal_mprotect_split(false); + test_seal_mprotect_split(true); + + test_seal_munmap(false); + test_seal_munmap(true); + test_seal_munmap_two_vma(false); + test_seal_munmap_two_vma(true); + test_seal_munmap_vma_with_gap(false); + test_seal_munmap_vma_with_gap(true); + + test_munmap_start_freed(false); + test_munmap_start_freed(true); + test_munmap_middle_freed(false); + test_munmap_middle_freed(true); + test_munmap_end_freed(false); + test_munmap_end_freed(true); + + test_seal_mremap_shrink(false); + test_seal_mremap_shrink(true); + test_seal_mremap_expand(false); + test_seal_mremap_expand(true); + test_seal_mremap_move(false); + test_seal_mremap_move(true); + + test_seal_mremap_shrink_fixed(false); + test_seal_mremap_shrink_fixed(true); + test_seal_mremap_expand_fixed(false); + test_seal_mremap_expand_fixed(true); + test_seal_mremap_move_fixed(false); + test_seal_mremap_move_fixed(true); + test_seal_mremap_move_dontunmap(false); + test_seal_mremap_move_dontunmap(true); + test_seal_mremap_move_fixed_zero(false); + test_seal_mremap_move_fixed_zero(true); + test_seal_mremap_move_dontunmap_anyaddr(false); + test_seal_mremap_move_dontunmap_anyaddr(true); + test_seal_discard_ro_anon(false); + test_seal_discard_ro_anon(true); + test_seal_discard_ro_anon_on_rw(false); + test_seal_discard_ro_anon_on_rw(true); + test_seal_discard_ro_anon_on_shared(false); + test_seal_discard_ro_anon_on_shared(true); + test_seal_discard_ro_anon_on_filebacked(false); + test_seal_discard_ro_anon_on_filebacked(true); + test_seal_mmap_overwrite_prot(false); + test_seal_mmap_overwrite_prot(true); + test_seal_mmap_expand(false); + test_seal_mmap_expand(true); + test_seal_mmap_shrink(false); + test_seal_mmap_shrink(true); + + test_seal_merge_and_split(); + test_seal_zero_address(); + + test_seal_discard_ro_anon_on_pkey(false); + test_seal_discard_ro_anon_on_pkey(true); + + ksft_finished(); + return 0; +}
From: Jeff Xu jeffxu@chromium.org
Add documentation for mseal().
Signed-off-by: Jeff Xu jeffxu@chromium.org --- Documentation/userspace-api/index.rst | 1 + Documentation/userspace-api/mseal.rst | 199 ++++++++++++++++++++++++++ 2 files changed, 200 insertions(+) create mode 100644 Documentation/userspace-api/mseal.rst
diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst index 09f61bd2ac2e..178f6a1d79cb 100644 --- a/Documentation/userspace-api/index.rst +++ b/Documentation/userspace-api/index.rst @@ -26,6 +26,7 @@ place where this information is gathered. iommu iommufd media/index + mseal netlink/index sysfs-platform_profile vduse diff --git a/Documentation/userspace-api/mseal.rst b/Documentation/userspace-api/mseal.rst new file mode 100644 index 000000000000..4132eec995a3 --- /dev/null +++ b/Documentation/userspace-api/mseal.rst @@ -0,0 +1,199 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Introduction of mseal +===================== + +:Author: Jeff Xu jeffxu@chromium.org + +Modern CPUs support memory permissions such as RW and NX bits. The memory +permission feature improves security stance on memory corruption bugs, i.e. +the attacker can’t just write to arbitrary memory and point the code to it, +the memory has to be marked with X bit, or else an exception will happen. + +Memory sealing additionally protects the mapping itself against +modifications. This is useful to mitigate memory corruption issues where a +corrupted pointer is passed to a memory management system. For example, +such an attacker primitive can break control-flow integrity guarantees +since read-only memory that is supposed to be trusted can become writable +or .text pages can get remapped. Memory sealing can automatically be +applied by the runtime loader to seal .text and .rodata pages and +applications can additionally seal security critical data at runtime. + +A similar feature already exists in the XNU kernel with the +VM_FLAGS_PERMANENT flag [1] and on OpenBSD with the mimmutable syscall [2]. + +User API +======== +mseal() +----------- +The mseal() syscall has the following signature: + +``int mseal(void addr, size_t len, unsigned long flags)`` + +**addr/len**: virtual memory address range. + +The address range set by ``addr``/``len`` must meet: + - The start address must be in an allocated VMA. + - The start address must be page aligned. + - The end address (``addr`` + ``len``) must be in an allocated VMA. + - no gap (unallocated memory) between start and end address. + +The ``len`` will be paged aligned implicitly by the kernel. + +**flags**: reserved for future use. + +**return values**: + +- ``0``: Success. + +- ``-EINVAL``: + - Invalid input ``flags``. + - The start address (``addr``) is not page aligned. + - Address range (``addr`` + ``len``) overflow. + +- ``-ENOMEM``: + - The start address (``addr``) is not allocated. + - The end address (``addr`` + ``len``) is not allocated. + - A gap (unallocated memory) between start and end address. + +- ``-EPERM``: + - sealing is supported only on 64-bit CPUs, 32-bit is not supported. + +- For above error cases, users can expect the given memory range is + unmodified, i.e. no partial update. + +- There might be other internal errors/cases not listed here, e.g. + error during merging/splitting VMAs, or the process reaching the max + number of supported VMAs. In those cases, partial updates to the given + memory range could happen. However, those cases should be rare. + +**Blocked operations after sealing**: + Unmapping, moving to another location, and shrinking the size, + via munmap() and mremap(), can leave an empty space, therefore + can be replaced with a VMA with a new set of attributes. + + Moving or expanding a different VMA into the current location, + via mremap(). + + Modifying a VMA via mmap(MAP_FIXED). + + Size expansion, via mremap(), does not appear to pose any + specific risks to sealed VMAs. It is included anyway because + the use case is unclear. In any case, users can rely on + merging to expand a sealed VMA. + + mprotect() and pkey_mprotect(). + + Some destructive madvice() behaviors (e.g. MADV_DONTNEED) + for anonymous memory, when users don't have write permission to the + memory. Those behaviors can alter region contents by discarding pages, + effectively a memset(0) for anonymous memory. + + Kernel will return -EPERM for blocked operations. + + For blocked operations, one can expect the given address is unmodified, + i.e. no partial update. Note, this is different from existing mm + system call behaviors, where partial updates are made till an error is + found and returned to userspace. To give an example: + + Assume following code sequence: + + - ptr = mmap(null, 8192, PROT_NONE); + - munmap(ptr + 4096, 4096); + - ret1 = mprotect(ptr, 8192, PROT_READ); + - mseal(ptr, 4096); + - ret2 = mprotect(ptr, 8192, PROT_NONE); + + ret1 will be -ENOMEM, the page from ptr is updated to PROT_READ. + + ret2 will be -EPERM, the page remains to be PROT_READ. + +**Note**: + +- mseal() only works on 64-bit CPUs, not 32-bit CPU. + +- users can call mseal() multiple times, mseal() on an already sealed memory + is a no-action (not error). + +- munseal() is not supported. + +Use cases: +========== +- glibc: + The dynamic linker, during loading ELF executables, can apply sealing to + non-writable memory segments. + +- Chrome browser: protect some security sensitive data-structures. + +Notes on which memory to seal: +============================== + +It might be important to note that sealing changes the lifetime of a mapping, +i.e. the sealed mapping won’t be unmapped till the process terminates or the +exec system call is invoked. Applications can apply sealing to any virtual +memory region from userspace, but it is crucial to thoroughly analyze the +mapping's lifetime prior to apply the sealing. + +For example: + +- aio/shm + + aio/shm can call mmap()/munmap() on behalf of userspace, e.g. ksys_shmdt() in + shm.c. The lifetime of those mapping are not tied to the lifetime of the + process. If those memories are sealed from userspace, then munmap() will fail, + causing leaks in VMA address space during the lifetime of the process. + +- Brk (heap) + + Currently, userspace applications can seal parts of the heap by calling + malloc() and mseal(). + let's assume following calls from user space: + + - ptr = malloc(size); + - mprotect(ptr, size, RO); + - mseal(ptr, size); + - free(ptr); + + Technically, before mseal() is added, the user can change the protection of + the heap by calling mprotect(RO). As long as the user changes the protection + back to RW before free(), the memory range can be reused. + + Adding mseal() into the picture, however, the heap is then sealed partially, + the user can still free it, but the memory remains to be RO. If the address + is re-used by the heap manager for another malloc, the process might crash + soon after. Therefore, it is important not to apply sealing to any memory + that might get recycled. + + Furthermore, even if the application never calls the free() for the ptr, + the heap manager may invoke the brk system call to shrink the size of the + heap. In the kernel, the brk-shrink will call munmap(). Consequently, + depending on the location of the ptr, the outcome of brk-shrink is + nondeterministic. + + +Additional notes: +================= +As Jann Horn pointed out in [3], there are still a few ways to write +to RO memory, which is, in a way, by design. Those cases are not covered +by mseal(). If applications want to block such cases, sandbox tools (such as +seccomp, LSM, etc) might be considered. + +Those cases are: + +- Write to read-only memory through /proc/self/mem interface. +- Write to read-only memory through ptrace (such as PTRACE_POKETEXT). +- userfaultfd. + +The idea that inspired this patch comes from Stephen Röttger’s work in V8 +CFI [4]. Chrome browser in ChromeOS will be the first user of this API. + +Reference: +========== +[1] https://github.com/apple-oss-distributions/xnu/blob/1031c584a5e37aff177559b9... + +[2] https://man.openbsd.org/mimmutable.2 + +[3] https://lore.kernel.org/lkml/CAG48ez3ShUYey+ZAFsU2i1RpQn0a5eOs2hzQ426FkcgnfU... + +[4] https://docs.google.com/document/d/1O2jwK4dxI3nRcOJuPYkonhTkNQfbmwdvxQMyXgea...
From: Jeff Xu jeffxu@chromium.org
Sealing read-only of elf mapping so it can't be changed by mprotect.
Signed-off-by: Jeff Xu jeffxu@chromium.org --- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + tools/testing/selftests/mm/seal_elf.c | 183 ++++++++++++++++++++++++++ 3 files changed, 185 insertions(+) create mode 100644 tools/testing/selftests/mm/seal_elf.c
diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index 76474c51c786..eff280b17a6e 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -47,3 +47,4 @@ mkdirty va_high_addr_switch hugetlb_fault_after_madv mseal_test +seal_elf diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index ba36a5c2b1fc..a0a12626cd19 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -60,6 +60,7 @@ TEST_GEN_FILES += mrelease_test TEST_GEN_FILES += mremap_dontunmap TEST_GEN_FILES += mremap_test TEST_GEN_FILES += mseal_test +TEST_GEN_FILES += seal_elf TEST_GEN_FILES += on-fault-limit TEST_GEN_FILES += pagemap_ioctl TEST_GEN_FILES += thuge-gen diff --git a/tools/testing/selftests/mm/seal_elf.c b/tools/testing/selftests/mm/seal_elf.c new file mode 100644 index 000000000000..61a2f1c94e02 --- /dev/null +++ b/tools/testing/selftests/mm/seal_elf.c @@ -0,0 +1,183 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <sys/mman.h> +#include <stdint.h> +#include <unistd.h> +#include <string.h> +#include <sys/time.h> +#include <sys/resource.h> +#include <stdbool.h> +#include "../kselftest.h" +#include <syscall.h> +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> +#include <assert.h> +#include <fcntl.h> +#include <assert.h> +#include <sys/ioctl.h> +#include <sys/vfs.h> +#include <sys/stat.h> + +/* + * need those definition for manually build using gcc. + * gcc -I ../../../../usr/include -DDEBUG -O3 -DDEBUG -O3 seal_elf.c -o seal_elf + */ +#define FAIL_TEST_IF_FALSE(c) do {\ + if (!(c)) {\ + ksft_test_result_fail("%s, line:%d\n", __func__, __LINE__);\ + goto test_end;\ + } \ + } \ + while (0) + +#define SKIP_TEST_IF_FALSE(c) do {\ + if (!(c)) {\ + ksft_test_result_skip("%s, line:%d\n", __func__, __LINE__);\ + goto test_end;\ + } \ + } \ + while (0) + + +#define TEST_END_CHECK() {\ + ksft_test_result_pass("%s\n", __func__);\ + return;\ +test_end:\ + return;\ +} + +#ifndef u64 +#define u64 unsigned long long +#endif + +/* + * define sys_xyx to call syscall directly. + */ +static int sys_mseal(void *start, size_t len) +{ + int sret; + + errno = 0; + sret = syscall(__NR_mseal, start, len, 0); + return sret; +} + +static void *sys_mmap(void *addr, unsigned long len, unsigned long prot, + unsigned long flags, unsigned long fd, unsigned long offset) +{ + void *sret; + + errno = 0; + sret = (void *) syscall(__NR_mmap, addr, len, prot, + flags, fd, offset); + return sret; +} + +inline int sys_mprotect(void *ptr, size_t size, unsigned long prot) +{ + int sret; + + errno = 0; + sret = syscall(__NR_mprotect, ptr, size, prot); + return sret; +} + +static bool seal_support(void) +{ + int ret; + void *ptr; + unsigned long page_size = getpagesize(); + + ptr = sys_mmap(NULL, page_size, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (ptr == (void *) -1) + return false; + + ret = sys_mseal(ptr, page_size); + if (ret < 0) + return false; + + return true; +} + +const char somestr[4096] = {"READONLY"}; + +static void test_seal_elf(void) +{ + int ret; + FILE *maps; + char line[512]; + int size = 0; + uintptr_t addr_start, addr_end; + char prot[5]; + char filename[256]; + unsigned long page_size = getpagesize(); + unsigned long long ptr = (unsigned long long) somestr; + char *somestr2 = (char *)somestr; + + /* + * Modify the protection of readonly somestr + */ + if (((unsigned long long)ptr % page_size) != 0) + ptr = (unsigned long long)ptr & ~(page_size - 1); + + ksft_print_msg("somestr = %s\n", somestr); + ksft_print_msg("change protection to rw\n"); + ret = sys_mprotect((void *)ptr, page_size, PROT_READ|PROT_WRITE); + FAIL_TEST_IF_FALSE(!ret); + *somestr2 = 'A'; + ksft_print_msg("somestr is modified to: %s\n", somestr); + ret = sys_mprotect((void *)ptr, page_size, PROT_READ); + FAIL_TEST_IF_FALSE(!ret); + + maps = fopen("/proc/self/maps", "r"); + FAIL_TEST_IF_FALSE(maps); + + /* + * apply sealing to elf binary + */ + while (fgets(line, sizeof(line), maps)) { + if (sscanf(line, "%lx-%lx %4s %*x %*x:%*x %*u %255[^\n]", + &addr_start, &addr_end, &prot, &filename) == 4) { + if (strlen(filename)) { + /* + * seal the mapping if read only. + */ + if (strstr(prot, "r-")) { + ret = sys_mseal((void *)addr_start, addr_end - addr_start); + FAIL_TEST_IF_FALSE(!ret); + ksft_print_msg("sealed: %lx-%lx %s %s\n", + addr_start, addr_end, prot, filename); + if ((uintptr_t) somestr >= addr_start && + (uintptr_t) somestr <= addr_end) + ksft_print_msg("mapping for somestr found\n"); + } + } + } + } + fclose(maps); + + ret = sys_mprotect((void *)ptr, page_size, PROT_READ | PROT_WRITE); + FAIL_TEST_IF_FALSE(ret < 0); + ksft_print_msg("somestr is sealed, mprotect is rejected\n"); + + TEST_END_CHECK(); +} + +int main(int argc, char **argv) +{ + bool test_seal = seal_support(); + + ksft_print_header(); + ksft_print_msg("pid=%d\n", getpid()); + + if (!test_seal) + ksft_exit_skip("sealing not supported, check CONFIG_64BIT\n"); + + ksft_set_plan(1); + + test_seal_elf(); + + ksft_finished(); + return 0; +}
linux-kselftest-mirror@lists.linaro.org
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jeffxu＠chromium.org