August 2025 - Linux-kselftest-mirror

[PATCH v3 0/7] selftests/mm: Fix false positives and skip unsupported tests

by Aboorva Devarajan

Hi all, This patch series addresses false positives in the generic mm selftests and skips tests that cannot run correctly due to missing features or system limitations. v2: https://lore.kernel.org/all/20250703060656.54345-1-aboorvad@linux.ibm.com/ Changes in v3: - Rebased onto the latest mm-new branch, top commit of the base is commit 0709ddf8951f ("mm: add zblock allocator"). - Minor refactor based on the review comments. - Included the tags from the previous version. --- v1: https://lore.kernel.org/all/20250616160632.35250-1-aboorvad@linux.ibm.com/ Changes in v2: - Rebased onto the mm-new branch, top commit of the base is commit 3b4a8ad89f7e ("mm: add zblock allocator"). - Split some patches for clarity. - Updated virtual_address_range test to support testing 4PB VA on PPC64. - Added proper Fixes: tags. - Included a patch to skip a failing userfaultfd test when unsupported, instead of reporting a failure. --- Please let us know if you have any further comments. Thanks, Aboorva Aboorva Devarajan (3): selftests/mm: Fix child process exit codes in ksm_functional_tests selftests/mm: Skip thuge-gen test if system is not setup properly selftests/mm: Skip hugepage-mremap test if userfaultfd unavailable Donet Tom (4): mm/selftests: Fix incorrect pointer being passed to mark_range() selftests/mm: Add support to test 4PB VA on PPC64 selftest/mm: Fix ksm_funtional_test failures mm/selftests: Fix split_huge_page_test failure on systems with 64KB page size tools/testing/selftests/mm/hugepage-mremap.c | 16 +++++++++-- .../selftests/mm/ksm_functional_tests.c | 28 +++++++++++++------ .../selftests/mm/split_huge_page_test.c | 23 +++++++++------ tools/testing/selftests/mm/thuge-gen.c | 11 +++++--- .../selftests/mm/virtual_address_range.c | 13 ++++++++- 5 files changed, 67 insertions(+), 24 deletions(-) -- 2.47.1

6 days, 8 hours

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[PATCH v2 0/1] selftests/futex: Check for shmget support at runtime

by Wake Liu

Changes in v2: - Restore RET_FAIL assignments in error paths to ensure the test's exit code accurately reflects the failure status. Wake Liu (1): selftests/futex: Check for shmget support at runtime .../selftests/futex/functional/futex_wait.c | 49 +++++++------ .../selftests/futex/functional/futex_waitv.c | 73 ++++++++++++------- 2 files changed, 73 insertions(+), 49 deletions(-) -- 2.50.1.703.g449372360f-goog

6 days, 16 hours

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[PATCH] selftests/filesystems/binderfs: Skip tests if user namespaces are unavailable

by Wake Liu

The binderfs selftests, specifically `binderfs_stress` and `binderfs_test_unprivileged`, depend on user namespaces to run. On kernels built without user namespace support (CONFIG_USER_NS=n), these tests will fail. To prevent these failures, add a check for the availability of user namespaces by testing for the existence of "/proc/self/ns/user". If the check fails, skip the tests and print an informative message. Signed-off-by: Wake Liu <wakel(a)google.com> --- .../selftests/filesystems/binderfs/binderfs_test.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c index 81db85a5cc16..e77ed34ebd06 100644 --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c @@ -291,6 +291,11 @@ static int write_id_mapping(enum idmap_type type, pid_t pid, const char *buf, return 0; } +static bool has_userns(void) +{ + return (access("/proc/self/ns/user", F_OK) == 0); +} + static void change_userns(struct __test_metadata *_metadata, int syncfds[2]) { int ret; @@ -378,6 +383,9 @@ static void *binder_version_thread(void *data) */ TEST(binderfs_stress) { + if (!has_userns()) + SKIP(return, "%s: user namespace not supported\n", __func__); + int fds[1000]; int syncfds[2]; pid_t pid; @@ -502,6 +510,8 @@ TEST(binderfs_test_privileged) TEST(binderfs_test_unprivileged) { + if (!has_userns()) + SKIP(return, "%s: user namespace not supported\n", __func__); int ret; int syncfds[2]; pid_t pid; -- 2.50.1.703.g449372360f-goog

6 days, 17 hours

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[PATCH] selftests/futex: Skip futex_waitv tests if ENOSYS

by Wake Liu

The futex_waitv() syscall was introduced in Linux 5.16. The existing test in futex_wait_timeout.c will fail on kernels older than 5.16 due to the syscall not being implemented. Modify the test_timeout() function to check if the error returned is ENOSYS. If it is, skip the test and report it as such, rather than failing. This ensures the selftests can be run on a wider range of kernel versions without false negatives. Signed-off-by: Wake Liu <wakel(a)google.com> --- .../selftests/futex/functional/futex_wait_timeout.c | 11 ++++++++--- .../testing/selftests/futex/functional/futex_waitv.c | 8 ++++++++ 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/futex/functional/futex_wait_timeout.c b/tools/testing/selftests/futex/functional/futex_wait_timeout.c index d183f878360b..323cab339814 100644 --- a/tools/testing/selftests/futex/functional/futex_wait_timeout.c +++ b/tools/testing/selftests/futex/functional/futex_wait_timeout.c @@ -64,9 +64,14 @@ void *get_pi_lock(void *arg) static void test_timeout(int res, int *ret, char *test_name, int err) { if (!res || errno != err) { - ksft_test_result_fail("%s returned %d\n", test_name, - res < 0 ? errno : res); - *ret = RET_FAIL; + if (errno == ENOSYS) { + ksft_test_result_skip("%s: %s\n", + test_name, strerror(errno)); + } else { + ksft_test_result_fail("%s returned %d\n", test_name, + res < 0 ? errno : res); + *ret = RET_FAIL; + } } else { ksft_test_result_pass("%s succeeds\n", test_name); } diff --git a/tools/testing/selftests/futex/functional/futex_waitv.c b/tools/testing/selftests/futex/functional/futex_waitv.c index 034dbfef40cb..2a86fd3ea657 100644 --- a/tools/testing/selftests/futex/functional/futex_waitv.c +++ b/tools/testing/selftests/futex/functional/futex_waitv.c @@ -59,6 +59,14 @@ void *waiterfn(void *arg) int main(int argc, char *argv[]) { + if (!ksft_min_kernel_version(5, 16)) { + ksft_print_header(); + ksft_set_plan(0); + ksft_print_msg("%s: FUTEX_WAITV not implemented until 5.16\n", + basename(argv[0])); + ksft_print_cnts(); + return KSFT_SKIP; + } pthread_t waiter; int res, ret = RET_PASS; struct timespec to; -- 2.50.1.703.g449372360f-goog

6 days, 18 hours

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[PATCH v3] selftests/futex: Check for shmget support at runtime

by Wake Liu

The futex tests `futex_wait.c` and `futex_waitv.c` rely on the `shmget()` syscall, which may not be available if the kernel is built without System V IPC support (CONFIG_SYSVIPC=n). This can lead to test failures on such systems. This patch modifies the tests to check for `shmget()` support at runtime by calling it and checking for an `ENOSYS` error. If `shmget()` is not supported, the tests are skipped with a clear message, improving the user experience and preventing false negatives. This approach is more robust than relying on compile-time checks and ensures that the tests run only when the required kernel features are present. Signed-off-by: Wake Liu <wakel(a)google.com> --- .../selftests/futex/functional/futex_wait.c | 57 ++++++++------- .../selftests/futex/functional/futex_waitv.c | 73 ++++++++++++------- 2 files changed, 78 insertions(+), 52 deletions(-) diff --git a/tools/testing/selftests/futex/functional/futex_wait.c b/tools/testing/selftests/futex/functional/futex_wait.c index 685140d9b93d..2a834f074959 100644 --- a/tools/testing/selftests/futex/functional/futex_wait.c +++ b/tools/testing/selftests/futex/functional/futex_wait.c @@ -48,7 +48,7 @@ static void *waiterfn(void *arg) int main(int argc, char *argv[]) { int res, ret = RET_PASS, fd, c, shm_id; - u_int32_t f_private = 0, *shared_data; + u_int32_t f_private = 0, *shared_data = NULL; unsigned int flags = FUTEX_PRIVATE_FLAG; pthread_t waiter; void *shm; @@ -96,32 +96,37 @@ int main(int argc, char *argv[]) /* Testing an anon page shared memory */ shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); if (shm_id < 0) { - perror("shmget"); - exit(1); - } - - shared_data = shmat(shm_id, NULL, 0); - - *shared_data = 0; - futex = shared_data; - - info("Calling shared (page anon) futex_wait on futex: %p\n", futex); - if (pthread_create(&waiter, NULL, waiterfn, NULL)) - error("pthread_create failed\n", errno); - - usleep(WAKE_WAIT_US); - - info("Calling shared (page anon) futex_wake on futex: %p\n", futex); - res = futex_wake(futex, 1, 0); - if (res != 1) { - ksft_test_result_fail("futex_wake shared (page anon) returned: %d %s\n", - errno, strerror(errno)); - ret = RET_FAIL; + if (errno == ENOSYS) { + ksft_test_result_skip("Kernel does not support System V shared memory\n"); + } else { + ksft_test_result_fail("shmget() failed with error: %s\n", strerror(errno)); + ret = RET_FAIL; + } } else { - ksft_test_result_pass("futex_wake shared (page anon) succeeds\n"); + shared_data = shmat(shm_id, NULL, 0); + + *shared_data = 0; + futex = shared_data; + + info("Calling shared (page anon) futex_wait on futex: %p\n", futex); + if (pthread_create(&waiter, NULL, waiterfn, NULL)) + error("pthread_create failed\n", errno); + + usleep(WAKE_WAIT_US); + + info("Calling shared (page anon) futex_wake on futex: %p\n", futex); + res = futex_wake(futex, 1, 0); + if (res != 1) { + if (res < 0) + ksft_test_result_fail("futex_wake shared (page anon) failed with res=%d: %m\n", res); + else + ksft_test_result_fail("futex_wake shared (page anon) returned %d, expected 1\n", res); + ret = RET_FAIL; + } else { + ksft_test_result_pass("futex_wake shared (page anon) succeeds\n"); + } } - /* Testing a file backed shared memory */ fd = open(SHM_PATH, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR); if (fd < 0) { @@ -161,7 +166,8 @@ int main(int argc, char *argv[]) } /* Freeing resources */ - shmdt(shared_data); + if (shared_data) + shmdt(shared_data); munmap(shm, sizeof(f_private)); remove(SHM_PATH); close(fd); @@ -169,3 +175,4 @@ int main(int argc, char *argv[]) ksft_print_cnts(); return ret; } + diff --git a/tools/testing/selftests/futex/functional/futex_waitv.c b/tools/testing/selftests/futex/functional/futex_waitv.c index a94337f677e1..034dbfef40cb 100644 --- a/tools/testing/selftests/futex/functional/futex_waitv.c +++ b/tools/testing/selftests/futex/functional/futex_waitv.c @@ -110,40 +110,58 @@ int main(int argc, char *argv[]) } /* Shared waitv */ - for (i = 0; i < NR_FUTEXES; i++) { - int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); - - if (shm_id < 0) { - perror("shmget"); - exit(1); + bool shm_supported = true; + int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); + + if (shm_id < 0) { + if (errno == ENOSYS) { + shm_supported = false; + ksft_test_result_skip("Kernel does not support System V shared memory\n"); + } else { + ksft_test_result_fail("shmget() failed with error: %s\n", strerror(errno)); + ret = RET_FAIL; + shm_supported = false; } + } else { + shmctl(shm_id, IPC_RMID, NULL); + } - unsigned int *shared_data = shmat(shm_id, NULL, 0); + if (shm_supported) { + for (i = 0; i < NR_FUTEXES; i++) { + int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); - *shared_data = 0; - waitv[i].uaddr = (uintptr_t)shared_data; - waitv[i].flags = FUTEX_32; - waitv[i].val = 0; - waitv[i].__reserved = 0; - } + if (shm_id < 0) { + perror("shmget"); + exit(1); + } - if (pthread_create(&waiter, NULL, waiterfn, NULL)) - error("pthread_create failed\n", errno); + unsigned int *shared_data = shmat(shm_id, NULL, 0); - usleep(WAKE_WAIT_US); + *shared_data = 0; + waitv[i].uaddr = (uintptr_t)shared_data; + waitv[i].flags = FUTEX_32; + waitv[i].val = 0; + waitv[i].__reserved = 0; + } - res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, 0); - if (res != 1) { - ksft_test_result_fail("futex_wake shared returned: %d %s\n", - res ? errno : res, - res ? strerror(errno) : ""); - ret = RET_FAIL; - } else { - ksft_test_result_pass("futex_waitv shared\n"); - } + if (pthread_create(&waiter, NULL, waiterfn, NULL)) + error("pthread_create failed\n", errno); - for (i = 0; i < NR_FUTEXES; i++) - shmdt(u64_to_ptr(waitv[i].uaddr)); + usleep(WAKE_WAIT_US); + + res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, 0); + if (res != 1) { + ksft_test_result_fail("futex_wake shared returned: %d %s\n", + res ? errno : res, + res ? strerror(errno) : ""); + ret = RET_FAIL; + } else { + ksft_test_result_pass("futex_waitv shared\n"); + } + + for (i = 0; i < NR_FUTEXES; i++) + shmdt(u64_to_ptr(waitv[i].uaddr)); + } /* Testing a waiter without FUTEX_32 flag */ waitv[0].flags = FUTEX_PRIVATE_FLAG; @@ -235,3 +253,4 @@ int main(int argc, char *argv[]) ksft_print_cnts(); return ret; } + -- 2.50.1.703.g449372360f-goog

6 days, 19 hours

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[PATCH RFC v2 0/2] KVM: arm64: PMU: Use multiple host PMUs

by Akihiko Odaki

On heterogeneous arm64 systems, KVM's PMU emulation is based on the features of a single host PMU instance. When a vCPU is migrated to a pCPU with an incompatible PMU, counters such as PMCCNTR_EL0 stop incrementing. Although this behavior is permitted by the architecture, Windows does not handle it gracefully and may crash with a division-by-zero error. The current workaround requires VMMs to pin vCPUs to a set of pCPUs that share a compatible PMU. This is difficult to implement correctly in QEMU/libvirt, where pinning occurs after vCPU initialization, and it also restricts the guest to a subset of available pCPUs. This patch introduces the KVM_ARM_VCPU_PMU_V3_COMPOSITION attribute to create a "composite" PMU. When set, KVM exposes a PMU that is compatible with all pCPUs by advertising only a single cycle counter, a feature common to all PMUs. This allows Windows guests to run reliably on heterogeneous systems without crashing, even without vCPU pinning, and enables VMMs to schedule vCPUs across all available pCPUs, making full use of the host hardware. A QEMU patch that demonstrates the usage of the new attribute is available at: https://lore.kernel.org/qemu-devel/20250806-kvm-v1-1-d1d50b7058cd@rsg.ci.i.… ("[PATCH RFC] target/arm/kvm: Choose PMU backend") Signed-off-by: Akihiko Odaki <odaki(a)rsg.ci.i.u-tokyo.ac.jp> --- Changes in v2: - Added the KVM_ARM_VCPU_PMU_V3_COMPOSITION attribute to opt in the feature. - Added code to handle overflow. - Link to v1: https://lore.kernel.org/r/20250319-hybrid-v1-1-4d1ada10e705@daynix.com --- Akihiko Odaki (2): KVM: arm64: PMU: Introduce KVM_ARM_VCPU_PMU_V3_COMPOSITION KVM: arm64: selftests: Test guest PMUv3 composition Documentation/virt/kvm/devices/vcpu.rst | 30 ++ arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/include/uapi/asm/kvm.h | 1 + arch/arm64/kvm/arm.c | 5 +- arch/arm64/kvm/pmu-emul.c | 495 +++++++++++++-------- arch/arm64/kvm/sys_regs.c | 2 +- include/kvm/arm_pmu.h | 12 +- .../selftests/kvm/arm64/vpmu_counter_access.c | 148 ++++-- 8 files changed, 461 insertions(+), 234 deletions(-) --- base-commit: 8ec6d99a41e3d1dbdff2bdb3aa42951681e1e76c change-id: 20250224-hybrid-01d5ff47edd2 Best regards, -- Akihiko Odaki <odaki(a)rsg.ci.i.u-tokyo.ac.jp>

6 days, 20 hours

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[PATCH v12 iproute2-next 0/3] DUALPI2 iproute2 patch

by chia-yu.chang＠nokia-bell-labs.com

From: Chia-Yu Chang <chia-yu.chang(a)nokia-bell-labs.com> Hello, Please find DUALPI2 iproute2 patch v12. For more details of DualPI2, please refer IETF RFC9332 (https://datatracker.ietf.org/doc/html/rfc9332). Best Regards, Chia-Yu --- v12 (04-Aug-2025) - Split into 3 patches: one move get_float(), one add get_float_min_max(), one for dualpi2 (David Ahern <dsahern(a)kernel.org>) - Repalce matches() with strcmp() within get_packets() (David Ahern <dsahern(a)kernel.org>) - Apply reverse xmas tree listing of variables (David Ahern <dsahern(a)kernel.org>) v11 (18-Jul-2025) - Replace TCA_DUALPI2 prefix with TC_DUALPI2 prefix for enums (Jakub Kicinski <kuba(a)kernel.org>) v10 (02-Jul-2025) - Replace STEP_THRESH and STEP_PACKETS w/ STEP_THRESH_PKTS and STEP_THRESH_US of net-next patch (Jakub Kicinski <kuba(a)kernel.org>) v9 (13-Jun-2025) - Fix space issue and typos (ALOK TIWARI <alok.a.tiwari(a)oracle.com>) - Change 'rtt_typical' to 'typical_rtt' in tc/q_dualpi2.c (ALOK TIWARI <alok.a.tiwari(a)oracle.com>) - Add the num of enum used by DualPI2 in pkt_sched.h v8 (09-May-2025) - Update pkt_sched.h with the one in nex-next - Correct a typo in the comment within pkt_sched.h (ALOK TIWARI <alok.a.tiwari(a)oracle.com>) - Update manual content in man/man8/tc-dualpi2.8 (ALOK TIWARI <alok.a.tiwari(a)oracle.com>) - Update tc/q_dualpi2.c to fix missing blank lines and add missing case (ALOK TIWARI <alok.a.tiwari(a)oracle.com>) v7 (05-May-2025) - Align pkt_sched.h with the v14 version of net-next due to spec modification in tc.yaml - Reorganize dualpi2_print_opt() to match the order in tc.yaml - Remove credit-queue in PRINT_JSON v6 (26-Apr-2025) - Update JSON file output due to spec modification in tc.yaml of net-next v5 (25-Mar-2025) - Use matches() to replace current strcmp() (Stephen Hemminger <stephen(a)networkplumber.org>) - Use general parse_percent() for handling scaled percentage values (Stephen Hemminger <stephen(a)networkplumber.org>) - Add print function for JSON of dualpi2 stats (Stephen Hemminger <stephen(a)networkplumber.org>) v4 (16-Mar-2025) - Add min_qlen_step to the dualpi2 attribute as the minimum queue length in number of packets in the L-queue to start step marking. v3 (21-Feb-2025) - Add memlimit to the dualpi2 attribute, and add memory_used, max_memory_used, and memory_limit in dualpi2 stats (Dave Taht <dave.taht(a)gmail.com>) - Update the manual to align with the latest implementation and clarify the queue naming and default unit - Use common "get_scaled_alpha_beta" and clean print_opt for Dualpi2 v2 (23-Oct-2024) - Rename get_float in dualpi2 to get_float_min_max in utils.c - Move get_float from iplink_can.c in utils.c (Stephen Hemminger <stephen(a)networkplumber.org>) - Add print function for JSON of dualpi2 (Stephen Hemminger <stephen(a)networkplumber.org>) --- Chia-Yu Chang (3): Move get_float() from ip/iplink_can.c to lib/utils.c Add get_float_min_max() in lib/utils.c tc: add dualpi2 scheduler module bash-completion/tc | 11 +- include/utils.h | 2 + ip/iplink_can.c | 14 -- lib/utils.c | 30 +++ man/man8/tc-dualpi2.8 | 249 ++++++++++++++++++++ tc/Makefile | 1 + tc/q_dualpi2.c | 535 ++++++++++++++++++++++++++++++++++++++++++ 7 files changed, 827 insertions(+), 15 deletions(-) create mode 100644 man/man8/tc-dualpi2.8 create mode 100644 tc/q_dualpi2.c -- 2.34.1

1 week

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[PATCH v19 00/27] riscv control-flow integrity for usermode

by Deepak Gupta

Basics and overview =================== Software with larger attack surfaces (e.g. network facing apps like databases, browsers or apps relying on browser runtimes) suffer from memory corruption issues which can be utilized by attackers to bend control flow of the program to eventually gain control (by making their payload executable). Attackers are able to perform such attacks by leveraging call-sites which rely on indirect calls or return sites which rely on obtaining return address from stack memory. To mitigate such attacks, risc-v extension zicfilp enforces that all indirect calls must land on a landing pad instruction `lpad` else cpu will raise software check exception (a new cpu exception cause code on riscv). Similarly for return flow, risc-v extension zicfiss extends architecture with - `sspush` instruction to push return address on a shadow stack - `sspopchk` instruction to pop return address from shadow stack and compare with input operand (i.e. return address on stack) - `sspopchk` to raise software check exception if comparision above was a mismatch - Protection mechanism using which shadow stack is not writeable via regular store instructions More information an details can be found at extensions github repo [1]. Equivalent to landing pad (zicfilp) on x86 is `ENDBRANCH` instruction in Intel CET [3] and branch target identification (BTI) [4] on arm. Similarly x86's Intel CET has shadow stack [5] and arm64 has guarded control stack (GCS) [6] which are very similar to risc-v's zicfiss shadow stack. x86 and arm64 support for user mode shadow stack is already in mainline. Kernel awareness for user control flow integrity ================================================ This series picks up Samuel Holland's envcfg changes [2] as well. So if those are being applied independently, they should be removed from this series. Enabling: In order to maintain compatibility and not break anything in user mode, kernel doesn't enable control flow integrity cpu extensions on binary by default. Instead exposes a prctl interface to enable, disable and lock the shadow stack or landing pad feature for a task. This allows userspace (loader) to enumerate if all objects in its address space are compiled with shadow stack and landing pad support and accordingly enable the feature. Additionally if a subsequent `dlopen` happens on a library, user mode can take a decision again to disable the feature (if incoming library is not compiled with support) OR terminate the task (if user mode policy is strict to have all objects in address space to be compiled with control flow integirty cpu feature). prctl to enable shadow stack results in allocating shadow stack from virtual memory and activating for user address space. x86 and arm64 are also following same direction due to similar reason(s). clone/fork: On clone and fork, cfi state for task is inherited by child. Shadow stack is part of virtual memory and is a writeable memory from kernel perspective (writeable via a restricted set of instructions aka shadow stack instructions) Thus kernel changes ensure that this memory is converted into read-only when fork/clone happens and COWed when fault is taken due to sspush, sspopchk or ssamoswap. In case `CLONE_VM` is specified and shadow stack is to be enabled, kernel will automatically allocate a shadow stack for that clone call. map_shadow_stack: x86 introduced `map_shadow_stack` system call to allow user space to explicitly map shadow stack memory in its address space. It is useful to allocate shadow for different contexts managed by a single thread (green threads or contexts) risc-v implements this system call as well. signal management: If shadow stack is enabled for a task, kernel performs an asynchronous control flow diversion to deliver the signal and eventually expects userspace to issue sigreturn so that original execution can be resumed. Even though resume context is prepared by kernel, it is in user space memory and is subject to memory corruption and corruption bugs can be utilized by attacker in this race window to perform arbitrary sigreturn and eventually bypass cfi mechanism. Another issue is how to ensure that cfi related state on sigcontext area is not trampled by legacy apps or apps compiled with old kernel headers. In order to mitigate control-flow hijacting, kernel prepares a token and place it on shadow stack before signal delivery and places address of token in sigcontext structure. During sigreturn, kernel obtains address of token from sigcontext struture, reads token from shadow stack and validates it and only then allow sigreturn to succeed. Compatiblity issue is solved by adopting dynamic sigcontext management introduced for vector extension. This series re-factor the code little bit to allow future sigcontext management easy (as proposed by Andy Chiu from SiFive) config and compilation: Introduce a new risc-v config option `CONFIG_RISCV_USER_CFI`. Selecting this config option picks the kernel support for user control flow integrity. This optin is presented only if toolchain has shadow stack and landing pad support. And is on purpose guarded by toolchain support. Reason being that eventually vDSO also needs to be compiled in with shadow stack and landing pad support. vDSO compile patches are not included as of now because landing pad labeling scheme is yet to settle for usermode runtime. To get more information on kernel interactions with respect to zicfilp and zicfiss, patch series adds documentation for `zicfilp` and `zicfiss` in following: Documentation/arch/riscv/zicfiss.rst Documentation/arch/riscv/zicfilp.rst How to test this series ======================= Toolchain --------- $ git clone git@github.com:sifive/riscv-gnu-toolchain.git -b cfi-dev $ riscv-gnu-toolchain/configure --prefix=<path-to-where-to-build> --with-arch=rv64gc_zicfilp_zicfiss --enable-linux --disable-gdb --with-extra-multilib-test="rv64gc_zicfilp_zicfiss-lp64d:-static" $ make -j$(nproc) Qemu ---- Get the lastest qemu $ cd qemu $ mkdir build $ cd build $ ../configure --target-list=riscv64-softmmu $ make -j$(nproc) Opensbi ------- $ git clone git@github.com:deepak0414/opensbi.git -b v6_cfi_spec_split_opensbi $ make CROSS_COMPILE=<your riscv toolchain> -j$(nproc) PLATFORM=generic Linux ----- Running defconfig is fine. CFI is enabled by default if the toolchain supports it. $ make ARCH=riscv CROSS_COMPILE=<path-to-cfi-riscv-gnu-toolchain>/build/bin/riscv64-unknown-linux-gnu- -j$(nproc) defconfig $ make ARCH=riscv CROSS_COMPILE=<path-to-cfi-riscv-gnu-toolchain>/build/bin/riscv64-unknown-linux-gnu- -j$(nproc) In case you're building your own rootfs using toolchain, please make sure you pick following patch to ensure that vDSO compiled with lpad and shadow stack. "arch/riscv: compile vdso with landing pad" Branch where above patch can be picked https://github.com/deepak0414/linux-riscv-cfi/tree/vdso_user_cfi_v6.12-rc1 Running ------- Modify your qemu command to have: -bios <path-to-cfi-opensbi>/build/platform/generic/firmware/fw_dynamic.bin -cpu rv64,zicfilp=true,zicfiss=true,zimop=true,zcmop=true vDSO related Opens (in the flux) ================================= I am listing these opens for laying out plan and what to expect in future patch sets. And of course for the sake of discussion. Shadow stack and landing pad enabling in vDSO ---------------------------------------------- vDSO must have shadow stack and landing pad support compiled in for task to have shadow stack and landing pad support. This patch series doesn't enable that (yet). Enabling shadow stack support in vDSO should be straight forward (intend to do that in next versions of patch set). Enabling landing pad support in vDSO requires some collaboration with toolchain folks to follow a single label scheme for all object binaries. This is necessary to ensure that all indirect call-sites are setting correct label and target landing pads are decorated with same label scheme. How many vDSOs --------------- Shadow stack instructions are carved out of zimop (may be operations) and if CPU doesn't implement zimop, they're illegal instructions. Kernel could be running on a CPU which may or may not implement zimop. And thus kernel will have to carry 2 different vDSOs and expose the appropriate one depending on whether CPU implements zimop or not. References ========== [1] - https://github.com/riscv/riscv-cfi [2] - https://lore.kernel.org/all/20240814081126.956287-1-samuel.holland@sifive.c… [3] - https://lwn.net/Articles/889475/ [4] - https://developer.arm.com/documentation/109576/0100/Branch-Target-Identific… [5] - https://www.intel.com/content/dam/develop/external/us/en/documents/catc17-i… [6] - https://lwn.net/Articles/940403/ To: Thomas Gleixner <tglx(a)linutronix.de> To: Ingo Molnar <mingo(a)redhat.com> To: Borislav Petkov <bp(a)alien8.de> To: Dave Hansen <dave.hansen(a)linux.intel.com> To: x86(a)kernel.org To: H. Peter Anvin <hpa(a)zytor.com> To: Andrew Morton <akpm(a)linux-foundation.org> To: Liam R. Howlett <Liam.Howlett(a)oracle.com> To: Vlastimil Babka <vbabka(a)suse.cz> To: Lorenzo Stoakes <lorenzo.stoakes(a)oracle.com> To: Paul Walmsley <paul.walmsley(a)sifive.com> To: Palmer Dabbelt <palmer(a)dabbelt.com> To: Albert Ou <aou(a)eecs.berkeley.edu> To: Conor Dooley <conor(a)kernel.org> To: Rob Herring <robh(a)kernel.org> To: Krzysztof Kozlowski <krzk+dt(a)kernel.org> To: Arnd Bergmann <arnd(a)arndb.de> To: Christian Brauner <brauner(a)kernel.org> To: Peter Zijlstra <peterz(a)infradead.org> To: Oleg Nesterov <oleg(a)redhat.com> To: Eric Biederman <ebiederm(a)xmission.com> To: Kees Cook <kees(a)kernel.org> To: Jonathan Corbet <corbet(a)lwn.net> To: Shuah Khan <shuah(a)kernel.org> To: Jann Horn <jannh(a)google.com> To: Conor Dooley <conor+dt(a)kernel.org> To: Miguel Ojeda <ojeda(a)kernel.org> To: Alex Gaynor <alex.gaynor(a)gmail.com> To: Boqun Feng <boqun.feng(a)gmail.com> To: Gary Guo <gary(a)garyguo.net> To: Björn Roy Baron <bjorn3_gh(a)protonmail.com> To: Benno Lossin <benno.lossin(a)proton.me> To: Andreas Hindborg <a.hindborg(a)kernel.org> To: Alice Ryhl <aliceryhl(a)google.com> To: Trevor Gross <tmgross(a)umich.edu> Cc: linux-kernel(a)vger.kernel.org Cc: linux-fsdevel(a)vger.kernel.org Cc: linux-mm(a)kvack.org Cc: linux-riscv(a)lists.infradead.org Cc: devicetree(a)vger.kernel.org Cc: linux-arch(a)vger.kernel.org Cc: linux-doc(a)vger.kernel.org Cc: linux-kselftest(a)vger.kernel.org Cc: alistair.francis(a)wdc.com Cc: richard.henderson(a)linaro.org Cc: jim.shu(a)sifive.com Cc: andybnac(a)gmail.com Cc: kito.cheng(a)sifive.com Cc: charlie(a)rivosinc.com Cc: atishp(a)rivosinc.com Cc: evan(a)rivosinc.com Cc: cleger(a)rivosinc.com Cc: alexghiti(a)rivosinc.com Cc: samitolvanen(a)google.com Cc: broonie(a)kernel.org Cc: rick.p.edgecombe(a)intel.com Cc: rust-for-linux(a)vger.kernel.org changelog --------- v19: - riscv_nousercfi was `int`. changed it to unsigned long. Thanks to Alex Ghiti for reporting it. It was a bug. - ELP is cleared on trap entry only when CONFIG_64BIT. - restore ssp back on return to usermode was being done before `riscv_v_context_nesting_end` on trap exit path. If kernel shadow stack were enabled this would result in kernel operating on user shadow stack and panic (as I found in my testing of kcfi patch series). So fixed that. v18: - rebased on 6.16-rc1 - uprobe handling clears ELP in sstatus image in pt_regs - vdso was missing shadow stack elf note for object files. added that. Additional asm file for vdso needed the elf marker flag. toolchain should complain if `-fcf-protection=full` and marker is missing for object generated from asm file. Asked toolchain folks to fix this. Although no reason to gate the merge on that. - Split up compile options for march and fcf-protection in vdso Makefile - CONFIG_RISCV_USER_CFI option is moved under "Kernel features" menu Added `arch/riscv/configs/hardening.config` fragment which selects CONFIG_RISCV_USER_CFI v17: - fixed warnings due to empty macros in usercfi.h (reported by alexg) - fixed prefixes in commit titles reported by alexg - took below uprobe with fcfi v2 patch from Zong Li and squashed it with "riscv/traps: Introduce software check exception and uprobe handling" https://lore.kernel.org/all/20250604093403.10916-1-zong.li@sifive.com/ v16: - If FWFT is not implemented or returns error for shadow stack activation, then no_usercfi is set to disable shadow stack. Although this should be picked up by extension validation and activation. Fixed this bug for zicfilp and zicfiss both. Thanks to Charlie Jenkins for reporting this. - If toolchain doesn't support cfi, cfi kselftest shouldn't build. Suggested by Charlie Jenkins. - Default for CONFIG_RISCV_USER_CFI is set to no. Charlie/Atish suggested to keep it off till we have more hardware availibility with RVA23 profile and zimop/zcmop implemented. Else this will start breaking people's workflow - Includes the fix if "!RV64 and !SBI" then definitions for FWFT in asm-offsets.c error. v15: - Toolchain has been updated to include `-fcf-protection` flag. This exists for x86 as well. Updated kernel patches to compile vDSO and selftest to compile with `fcf-protection=full` flag. - selecting CONFIG_RISCV_USERCFI selects CONFIG_RISCV_SBI. - Patch to enable shadow stack for kernel wasn't hidden behind CONFIG_RISCV_USERCFI and CONFIG_RISCV_SBI. fixed that. v14: - rebased on top of palmer/sbi-v3. Thus dropped clement's FWFT patches Updated RISCV_ISA_EXT_XXXX in hwcap and hwprobe constants. - Took Radim's suggestions on bitfields. - Placed cfi_state at the end of thread_info block so that current situation is not disturbed with respect to member fields of thread_info in single cacheline. v13: - cpu_supports_shadow_stack/cpu_supports_indirect_br_lp_instr uses riscv_has_extension_unlikely() - uses nops(count) to create nop slide - RISCV_ACQUIRE_BARRIER is not needed in `amo_user_shstk`. Removed it - changed ternaries to simply use implicit casting to convert to bool. - kernel command line allows to disable zicfilp and zicfiss independently. updated kernel-parameters.txt. - ptrace user abi for cfi uses bitmasks instead of bitfields. Added ptrace kselftest. - cosmetic and grammatical changes to documentation. v12: - It seems like I had accidently squashed arch agnostic indirect branch tracking prctl and riscv implementation of those prctls. Split them again. - set_shstk_status/set_indir_lp_status perform CSR writes only when CPU support is available. As suggested by Zong Li. - Some minor clean up in kselftests as suggested by Zong Li. v11: - patch "arch/riscv: compile vdso with landing pad" was unconditionally selecting `_zicfilp` for vDSO compile. fixed that. Changed `lpad 1` to to `lpad 0`. v10: - dropped "mm: helper `is_shadow_stack_vma` to check shadow stack vma". This patch is not that interesting to this patch series for risc-v. There are instances in arch directories where VM_SHADOW_STACK flag is anyways used. Dropping this patch to expedite merging in riscv tree. - Took suggestions from `Clement` on "riscv: zicfiss / zicfilp enumeration" to validate presence of cfi based on config. - Added a patch for vDSO to have `lpad 0`. I had omitted this earlier to make sure we add single vdso object with cfi enabled. But a vdso object with scheme of zero labeled landing pad is least common denominator and should work with all objects of zero labeled as well as function-signature labeled objects. v9: - rebased on master (39a803b754d5 fix braino in "9p: fix ->rename_sem exclusion") - dropped "mm: Introduce ARCH_HAS_USER_SHADOW_STACK" (master has it from arm64/gcs) - dropped "prctl: arch-agnostic prctl for shadow stack" (master has it from arm64/gcs) v8: - rebased on palmer/for-next - dropped samuel holland's `envcfg` context switch patches. they are in parlmer/for-next v7: - Removed "riscv/Kconfig: enable HAVE_EXIT_THREAD for riscv" Instead using `deactivate_mm` flow to clean up. see here for more context https://lore.kernel.org/all/20230908203655.543765-1-rick.p.edgecombe@intel.… - Changed the header include in `kselftest`. Hopefully this fixes compile issue faced by Zong Li at SiFive. - Cleaned up an orphaned change to `mm/mmap.c` in below patch "riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE" - Lock interfaces for shadow stack and indirect branch tracking expect arg == 0 Any future evolution of this interface should accordingly define how arg should be setup. - `mm/map.c` has an instance of using `VM_SHADOW_STACK`. Fixed it to use helper `is_shadow_stack_vma`. - Link to v6: https://lore.kernel.org/r/20241008-v5_user_cfi_series-v6-0-60d9fe073f37@riv… v6: - Picked up Samuel Holland's changes as is with `envcfg` placed in `thread` instead of `thread_info` - fixed unaligned newline escapes in kselftest - cleaned up messages in kselftest and included test output in commit message - fixed a bug in clone path reported by Zong Li - fixed a build issue if CONFIG_RISCV_ISA_V is not selected (this was introduced due to re-factoring signal context management code) v5: - rebased on v6.12-rc1 - Fixed schema related issues in device tree file - Fixed some of the documentation related issues in zicfilp/ss.rst (style issues and added index) - added `SHADOW_STACK_SET_MARKER` so that implementation can define base of shadow stack. - Fixed warnings on definitions added in usercfi.h when CONFIG_RISCV_USER_CFI is not selected. - Adopted context header based signal handling as proposed by Andy Chiu - Added support for enabling kernel mode access to shadow stack using FWFT (https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/src/ext-firmware…) - Link to v5: https://lore.kernel.org/r/20241001-v5_user_cfi_series-v1-0-3ba65b6e550f@riv… (Note: I had an issue in my workflow due to which version number wasn't picked up correctly while sending out patches) v4: - rebased on 6.11-rc6 - envcfg: Converged with Samuel Holland's patches for envcfg management on per- thread basis. - vma_is_shadow_stack is renamed to is_vma_shadow_stack - picked up Mark Brown's `ARCH_HAS_USER_SHADOW_STACK` patch - signal context: using extended context management to maintain compatibility. - fixed `-Wmissing-prototypes` compiler warnings for prctl functions - Documentation fixes and amending typos. - Link to v4: https://lore.kernel.org/all/20240912231650.3740732-1-debug@rivosinc.com/ v3: - envcfg logic to pick up base envcfg had a bug where `ENVCFG_CBZE` could have been picked on per task basis, even though CPU didn't implement it. Fixed in this series. - dt-bindings As suggested, split into separate commit. fixed the messaging that spec is in public review - arch_is_shadow_stack change arch_is_shadow_stack changed to vma_is_shadow_stack - hwprobe zicfiss / zicfilp if present will get enumerated in hwprobe - selftests As suggested, added object and binary filenames to .gitignore Selftest binary anyways need to be compiled with cfi enabled compiler which will make sure that landing pad and shadow stack are enabled. Thus removed separate enable/disable tests. Cleaned up tests a bit. - Link to v3: https://lore.kernel.org/lkml/20240403234054.2020347-1-debug@rivosinc.com/ v2: - Using config `CONFIG_RISCV_USER_CFI`, kernel support for riscv control flow integrity for user mode programs can be compiled in the kernel. - Enabling of control flow integrity for user programs is left to user runtime - This patch series introduces arch agnostic `prctls` to enable shadow stack and indirect branch tracking. And implements them on riscv. --- Changes in v19: - Link to v18: https://lore.kernel.org/r/20250711-v5_user_cfi_series-v18-0-a8ee62f9f38e@ri… Changes in v18: - Link to v17: https://lore.kernel.org/r/20250604-v5_user_cfi_series-v17-0-4565c2cf869f@ri… Changes in v17: - Link to v16: https://lore.kernel.org/r/20250522-v5_user_cfi_series-v16-0-64f61a35eee7@ri… Changes in v16: - Link to v15: https://lore.kernel.org/r/20250502-v5_user_cfi_series-v15-0-914966471885@ri… Changes in v15: - changelog posted just below cover letter - Link to v14: https://lore.kernel.org/r/20250429-v5_user_cfi_series-v14-0-5239410d012a@ri… Changes in v14: - changelog posted just below cover letter - Link to v13: https://lore.kernel.org/r/20250424-v5_user_cfi_series-v13-0-971437de586a@ri… Changes in v13: - changelog posted just below cover letter - Link to v12: https://lore.kernel.org/r/20250314-v5_user_cfi_series-v12-0-e51202b53138@ri… Changes in v12: - changelog posted just below cover letter - Link to v11: https://lore.kernel.org/r/20250310-v5_user_cfi_series-v11-0-86b36cbfb910@ri… Changes in v11: - changelog posted just below cover letter - Link to v10: https://lore.kernel.org/r/20250210-v5_user_cfi_series-v10-0-163dcfa31c60@ri… --- Andy Chiu (1): riscv: signal: abstract header saving for setup_sigcontext Deepak Gupta (25): mm: VM_SHADOW_STACK definition for riscv dt-bindings: riscv: zicfilp and zicfiss in dt-bindings (extensions.yaml) riscv: zicfiss / zicfilp enumeration riscv: zicfiss / zicfilp extension csr and bit definitions riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE riscv/mm: manufacture shadow stack pte riscv/mm: teach pte_mkwrite to manufacture shadow stack PTEs riscv/mm: write protect and shadow stack riscv/mm: Implement map_shadow_stack() syscall riscv/shstk: If needed allocate a new shadow stack on clone riscv: Implements arch agnostic shadow stack prctls prctl: arch-agnostic prctl for indirect branch tracking riscv: Implements arch agnostic indirect branch tracking prctls riscv/traps: Introduce software check exception and uprobe handling riscv/signal: save and restore of shadow stack for signal riscv/kernel: update __show_regs to print shadow stack register riscv/ptrace: riscv cfi status and state via ptrace and in core files riscv/hwprobe: zicfilp / zicfiss enumeration in hwprobe riscv: kernel command line option to opt out of user cfi riscv: enable kernel access to shadow stack memory via FWFT sbi call riscv: create a config for shadow stack and landing pad instr support riscv: Documentation for landing pad / indirect branch tracking riscv: Documentation for shadow stack on riscv kselftest/riscv: kselftest for user mode cfi Jim Shu (1): arch/riscv: compile vdso with landing pad and shadow stack note Documentation/admin-guide/kernel-parameters.txt | 8 + Documentation/arch/riscv/index.rst | 2 + Documentation/arch/riscv/zicfilp.rst | 115 +++++ Documentation/arch/riscv/zicfiss.rst | 179 +++++++ .../devicetree/bindings/riscv/extensions.yaml | 14 + arch/riscv/Kconfig | 21 + arch/riscv/Makefile | 5 +- arch/riscv/configs/hardening.config | 4 + arch/riscv/include/asm/asm-prototypes.h | 1 + arch/riscv/include/asm/assembler.h | 44 ++ arch/riscv/include/asm/cpufeature.h | 12 + arch/riscv/include/asm/csr.h | 16 + arch/riscv/include/asm/entry-common.h | 2 + arch/riscv/include/asm/hwcap.h | 2 + arch/riscv/include/asm/mman.h | 26 + arch/riscv/include/asm/mmu_context.h | 7 + arch/riscv/include/asm/pgtable.h | 30 +- arch/riscv/include/asm/processor.h | 1 + arch/riscv/include/asm/thread_info.h | 3 + arch/riscv/include/asm/usercfi.h | 95 ++++ arch/riscv/include/asm/vector.h | 3 + arch/riscv/include/uapi/asm/hwprobe.h | 2 + arch/riscv/include/uapi/asm/ptrace.h | 34 ++ arch/riscv/include/uapi/asm/sigcontext.h | 1 + arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/asm-offsets.c | 10 + arch/riscv/kernel/cpufeature.c | 27 + arch/riscv/kernel/entry.S | 38 ++ arch/riscv/kernel/head.S | 27 + arch/riscv/kernel/process.c | 27 +- arch/riscv/kernel/ptrace.c | 95 ++++ arch/riscv/kernel/signal.c | 148 +++++- arch/riscv/kernel/sys_hwprobe.c | 2 + arch/riscv/kernel/sys_riscv.c | 10 + arch/riscv/kernel/traps.c | 54 ++ arch/riscv/kernel/usercfi.c | 545 +++++++++++++++++++++ arch/riscv/kernel/vdso/Makefile | 11 +- arch/riscv/kernel/vdso/flush_icache.S | 4 + arch/riscv/kernel/vdso/getcpu.S | 4 + arch/riscv/kernel/vdso/rt_sigreturn.S | 4 + arch/riscv/kernel/vdso/sys_hwprobe.S | 4 + arch/riscv/kernel/vdso/vgetrandom-chacha.S | 5 +- arch/riscv/mm/init.c | 2 +- arch/riscv/mm/pgtable.c | 16 + include/linux/cpu.h | 4 + include/linux/mm.h | 7 + include/uapi/linux/elf.h | 2 + include/uapi/linux/prctl.h | 27 + kernel/sys.c | 30 ++ tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/cfi/.gitignore | 3 + tools/testing/selftests/riscv/cfi/Makefile | 16 + tools/testing/selftests/riscv/cfi/cfi_rv_test.h | 82 ++++ tools/testing/selftests/riscv/cfi/riscv_cfi_test.c | 173 +++++++ tools/testing/selftests/riscv/cfi/shadowstack.c | 385 +++++++++++++++ tools/testing/selftests/riscv/cfi/shadowstack.h | 27 + 56 files changed, 2389 insertions(+), 30 deletions(-) --- base-commit: a2a05801de77ca5122fc34e3eb84d6359ef70389 change-id: 20240930-v5_user_cfi_series-3dc332f8f5b2 -- - 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[RFC PATCH 00/18] cgroup/cpuset: Enable runtime modification of

by Waiman Long

The "nohz_full" and "rcu_nocbs" boot command parameters can be used to remove a lot of kernel overhead on a specific set of isolated CPUs which can be used to run some latency/bandwidth sensitive workloads with as little kernel disturbance/noise as possible. The problem with this mode of operation is the fact that it is a static configuration which cannot be changed after boot to adjust for changes in application loading. There is always a desire to enable runtime modification of the number of isolated CPUs that can be dedicated to this type of demanding workloads. This patchset is an attempt to do just that with an amount of CPU isolation close to what can be done with the nohz_full and rcu_nocbs boot kernel parameters. This patch series provides the ability to change the set of housekeeping CPUs at run time via the cpuset isolated partition functionality. Currently, the cpuset isolated partition is able to disable scheduler load balancing and the CPU affinity of the unbound workqueue to avoid the isolated CPUs. This patch series will extend that with other kernel noises associated with the nohz_full boot command line parameter which has the following sub-categories: - tick - timer - RCU - MISC - WQ - kthread The rcu_nocbs is actually a subset of nohz_full focusing just on the RCU part of the kernel noises. The WQ part has already been handled by the current cpuset code. This series focuses on the tick and RCU part of the kernel noises by actively changing their internal data structures to track changes in the list of isolated CPUs used by cpuset isolated partitions. The dynamic update of the lists of housekeeping CPUs at run time will also have impact on the other part of the kernel noises that reference the lists of housekeeping CPUs at run time. The pending patch series on timer migration[1], when properly integrated will support the timer part too. The CPU hotplug functionality of the Linux kernel is used to facilitate the runtime change of the nohz_full isolated CPUs with minimal code changes. The CPUs that need to be switched from non-isolated to isolated or vice versa will be brought offline first, making the necessary changes and then brought back online afterward. The use of CPU hotplug, however, does have a slight drawback of freezing all the other CPUs in part of the offlining process using the stop machine feature of the kernel. That will cause a noticeable latency spikes in other running applications which may be significant to sensitive applications running on isolated CPUs in other isolated partitions at the time. Hopefully we can find a way to solve this problem in the future. One possible workaround for this is to reserve a set of nohz_full isolated CPUs at boot time using the nohz_full boot command parameter. The bringing of those nohz_full reserved CPUs into and out of isolated partitions will not invoke CPU hotplug and hence will not cause unexpected latency spikes. These reserved CPUs will only be needed if there are other existing isolated partitions running critical applications at the time when an isolated partition needs to be created. Patches 1-4 updates the CPU isolation code at kernel/sched/isolation.c to enable dynamic update of the lists of housekeeping CPUs. Patch 5 introduces a new cpuhp_offline_cb() API for shutting down the given set of CPUs, running the given callback method and then bringing those CPUs back online again. This new API will block any incoming hotplug events from interfering this operation. Patches 6-9 updates the cpuset partition code to use the new cpuhp API to shut down the affect CPUs, making changes to the housekeeping cpumasks and then bring those CPUs online afterward. Patch 10 works around an issue in the DL server code that block the hotplug operation under certain configurations. Patch 11-14 updates the timer tick and related code to enable proper updates to the set of CPUs requiring nohz_full dynticks support. Patch 15 enables runtime modification to the set of isolated CPUs requiring RCU NO-CB CPU support with minor changes to the RCU code. Patches 16-18 includes other miscellaneous updates to cpuset code and documentation. This patch series is applied on top of some other cpuset patches[1] posted upstream recently. [1] https://lore.kernel.org/lkml/20250806093855.86469-1-gmonaco@redhat.com/ [2] https://lore.kernel.org/lkml/20250806172430.1155133-1-longman@redhat.com/ Waiman Long (18): sched/isolation: Enable runtime update of housekeeping cpumasks sched/isolation: Call sched_tick_offload_init() when HK_FLAG_KERNEL_NOISE is first set sched/isolation: Use RCU to delay successive housekeeping cpumask updates sched/isolation: Add a debugfs file to dump housekeeping cpumasks cpu/hotplug: Add a new cpuhp_offline_cb() API cgroup/cpuset: Introduce a new top level isolcpus_update_mutex cgroup/cpuset: Allow overwriting HK_TYPE_DOMAIN housekeeping cpumask cgroup/cpuset: Use CPU hotplug to enable runtime nohz_full modification cgroup/cpuset: Revert "Include isolated cpuset CPUs in cpu_is_isolated() check" sched/core: Ignore DL BW deactivation error if in cpuhp_offline_cb_mode tick/nohz: Make nohz_full parameter optional tick/nohz: Introduce tick_nohz_full_update_cpus() to update tick_nohz_full_mask tick/nohz: Allow runtime changes in full dynticks CPUs tick: Pass timer tick job to an online HK CPU in tick_cpu_dying() cgroup/cpuset: Enable RCU NO-CB CPU offloading of newly isolated CPUs cgroup/cpuset: Don't set have_boot_nohz_full without any boot time nohz_full CPU cgroup/cpuset: Documentation updates & don't use CPU 0 for isolated partition cgroup/cpuset: Add pr_debug() statements for cpuhp_offline_cb() call Documentation/admin-guide/cgroup-v2.rst | 33 +- .../admin-guide/kernel-parameters.txt | 19 +- include/linux/context_tracking.h | 8 +- include/linux/cpuhplock.h | 9 + include/linux/cpuset.h | 6 - include/linux/rcupdate.h | 2 + include/linux/sched/isolation.h | 9 +- include/linux/tick.h | 2 + kernel/cgroup/cpuset.c | 344 ++++++++++++------ kernel/context_tracking.c | 21 +- kernel/cpu.c | 47 +++ kernel/rcu/tree_nocb.h | 7 +- kernel/sched/core.c | 8 +- kernel/sched/debug.c | 32 ++ kernel/sched/isolation.c | 151 +++++++- kernel/sched/sched.h | 2 +- kernel/time/tick-common.c | 15 +- kernel/time/tick-sched.c | 24 +- .../selftests/cgroup/test_cpuset_prs.sh | 15 +- 19 files changed, 583 insertions(+), 171 deletions(-) -- 2.50.0

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[PATCH v4 0/4] procfs: make reference pidns more user-visible

by Aleksa Sarai

Ever since the introduction of pid namespaces, procfs has had very implicit behaviour surrounding them (the pidns used by a procfs mount is auto-selected based on the mounting process's active pidns, and the pidns itself is basically hidden once the mount has been constructed). /* pidns mount option for procfs */ This implicit behaviour has historically meant that userspace was required to do some special dances in order to configure the pidns of a procfs mount as desired. Examples include: * In order to bypass the mnt_too_revealing() check, Kubernetes creates a procfs mount from an empty pidns so that user namespaced containers can be nested (without this, the nested containers would fail to mount procfs). But this requires forking off a helper process because you cannot just one-shot this using mount(2). * Container runtimes in general need to fork into a container before configuring its mounts, which can lead to security issues in the case of shared-pidns containers (a privileged process in the pidns can interact with your container runtime process). While SUID_DUMP_DISABLE and user namespaces make this less of an issue, the strict need for this due to a minor uAPI wart is kind of unfortunate. Things would be much easier if there was a way for userspace to just specify the pidns they want. Patch 1 implements a new "pidns" argument which can be set using fsconfig(2): fsconfig(procfd, FSCONFIG_SET_FD, "pidns", NULL, nsfd); fsconfig(procfd, FSCONFIG_SET_STRING, "pidns", "/proc/self/ns/pid", 0); or classic mount(2) / mount(8): // mount -t proc -o pidns=/proc/self/ns/pid proc /tmp/proc mount("proc", "/tmp/proc", "proc", MS_..., "pidns=/proc/self/ns/pid"); The initial security model I have in this RFC is to be as conservative as possible and just mirror the security model for setns(2) -- which means that you can only set pidns=... to pid namespaces that your current pid namespace is a direct ancestor of and you have CAP_SYS_ADMIN privileges over the pid namespace. This fulfils the requirements of container runtimes, but I suspect that this may be too strict for some usecases. The pidns argument is not displayed in mountinfo -- it's not clear to me what value it would make sense to show (maybe we could just use ns_dname to provide an identifier for the namespace, but this number would be fairly useless to userspace). I'm open to suggestions. Note that PROCFS_GET_PID_NAMESPACE (see below) does at least let userspace get information about this outside of mountinfo. Note that you cannot change the pidns of an already-created procfs instance. The primary reason is that allowing this to be changed would require RCU-protecting proc_pid_ns(sb) and thus auditing all of fs/proc/* and some of the users in fs/* to make sure they wouldn't UAF the pid namespace. Since creating procfs instances is very cheap, it seems unnecessary to overcomplicate this upfront. Trying to reconfigure procfs this way errors out with -EBUSY. /* ioctl(PROCFS_GET_PID_NAMESPACE) */ In addition, being able to figure out what pid namespace is being used by a procfs mount is quite useful when you have an administrative process (such as a container runtime) which wants to figure out the correct way of mapping PIDs between its own namespace and the namespace for procfs (using NS_GET_{PID,TGID}_{IN,FROM}_PIDNS). There are alternative ways to do this, but they all rely on ancillary information that third-party libraries and tools do not necessarily have access to. To make this easier, add a new ioctl (PROCFS_GET_PID_NAMESPACE) which can be used to get a reference to the pidns that a procfs is using. Rather than copying the (fairly strict) security model for setns(2), apply a slightly looser model to better match what userspace can already do: * Make the ioctl only valid on the root (meaning that a process without access to the procfs root -- such as only having an fd to a procfs file or some open_tree(2)-like subset -- cannot use this API). This means that the process already has some level of access to the /proc/$pid directories. * If the calling process is in an ancestor pidns, then they can already create pidfd for processes inside the pidns, which is morally equivalent to a pidns file descriptor according to setns(2). So it seems reasonable to just allow it in this case. (The justification for this model was suggested by Christian.) * If the process has access to /proc/1/ns/pid already (i.e. has ptrace-read access to the pidns pid1), then this ioctl is equivalent to just opening a handle to it that way. Ideally we would check for ptrace-read access against all processes in the pidns (which is very likely to be true for at least one process, as SUID_DUMP_DISABLE is cleared on exec(2) and is rarely set by most programs), but this would obviously not scale. I'm open to suggestions for whether we need to make this stricter (or possibly allow more cases). Signed-off-by: Aleksa Sarai <cyphar(a)cyphar.com> --- Changes in v4: - Remove unneeded EXPORT_SYMBOL_GPL. [Christian Brauner] - Return -EOPNOTSUPP for new APIs for CONFIG_PID_NS=n rather than pretending they don't exist entirely. [Christian Brauner] - PROCFS_IOCTL_MAGIC conflicts with XSDFEC_MAGIC, so we need to allocate subvalues more carefully (switch to _IO(PROCFS_IOCTL_MAGIC, 32)). - Add some more selftests for PROCFS_GET_PID_NAMESPACE. - Reword argument for PROCFS_GET_PID_NAMESPACE security model based on Christian's suggestion, and remove CAP_SYS_ADMIN edge-case (in most cases, such a process would also have ptrace-read credentials over the pidns pid1). - v3: <https://lore.kernel.org/r/20250724-procfs-pidns-api-v3-0-4c685c910923@cypha…> Changes in v3: - Disallow changing pidns for existing procfs instances, as we'd probably have to RCU-protect everything that touches the pinned pidns reference. - Improve tests with slightly nicer ASSERT_ERRNO* macros. - v2: <https://lore.kernel.org/r/20250723-procfs-pidns-api-v2-0-621e7edd8e40@cypha…> Changes in v2: - #ifdef CONFIG_PID_NS - Improve cover letter wording to make it clear we're talking about two separate features with different permission models. [Andy Lutomirski] - Fix build warnings in pidns_is_ancestor() patch. [kernel test robot] - v1: <https://lore.kernel.org/r/20250721-procfs-pidns-api-v1-0-5cd9007e512d@cypha…> --- Aleksa Sarai (4): pidns: move is-ancestor logic to helper procfs: add "pidns" mount option procfs: add PROCFS_GET_PID_NAMESPACE ioctl selftests/proc: add tests for new pidns APIs Documentation/filesystems/proc.rst | 12 ++ fs/proc/root.c | 166 +++++++++++++++- include/linux/pid_namespace.h | 9 + include/uapi/linux/fs.h | 4 + kernel/pid_namespace.c | 22 ++- tools/testing/selftests/proc/.gitignore | 1 + tools/testing/selftests/proc/Makefile | 1 + tools/testing/selftests/proc/proc-pidns.c | 315 ++++++++++++++++++++++++++++++ 8 files changed, 514 insertions(+), 16 deletions(-) --- base-commit: 66639db858112bf6b0f76677f7517643d586e575 change-id: 20250717-procfs-pidns-api-8ed1583431f0 Best regards, -- Aleksa Sarai <cyphar(a)cyphar.com>

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