Hi,
As part of looking at what GCC plugins could be replaced with Clang implementations, this series uses the recently landed stack depth tracking callback in Clang[1] to implement the stackleak feature. Since the Clang feature is now landed, I'm moving this out of RFC to a v1.
Since this touches a lot of arch-specific Makefiles, I tried to trim the CC list down to just mailing lists in those cases, otherwise the CC was giant.
Thanks!
-Kees
[1] https://clang.llvm.org/docs/SanitizerCoverage.html#tracing-stack-depth
v1: - Finalize Clang URLs for landed feature - Perform CFLAGS enabling more sanely, as done for randstruct - Split __no_sanitize_coverage into separate patch - Update hardening.config and MAINTAINERS - Fix bug found with nvme tree RFC: https://lore.kernel.org/lkml/20250502185834.work.560-kees@kernel.org/
Kees Cook (8): nvme-pci: Make nvme_pci_npages_prp() __always_inline init.h: Disable sanitizer coverage for __init and __head stackleak: Rename CONFIG_GCC_PLUGIN_STACKLEAK to CONFIG_STACKLEAK stackleak: Rename stackleak_track_stack to __sanitizer_cov_stack_depth stackleak: Split STACKLEAK_CFLAGS from GCC_PLUGINS_CFLAGS stackleak: Support Clang stack depth tracking configs/hardening: Enable CONFIG_STACKLEAK configs/hardening: Enable CONFIG_INIT_ON_FREE_DEFAULT_ON
security/Kconfig.hardening | 25 ++++++---- Makefile | 1 + arch/arm/boot/compressed/Makefile | 2 +- arch/arm/vdso/Makefile | 2 +- arch/arm64/kernel/pi/Makefile | 2 +- arch/arm64/kernel/vdso/Makefile | 3 +- arch/arm64/kvm/hyp/nvhe/Makefile | 2 +- arch/riscv/kernel/pi/Makefile | 2 +- arch/riscv/purgatory/Makefile | 2 +- arch/sparc/vdso/Makefile | 3 +- arch/x86/entry/vdso/Makefile | 3 +- arch/x86/purgatory/Makefile | 2 +- drivers/firmware/efi/libstub/Makefile | 6 +-- kernel/Makefile | 4 +- lib/Makefile | 2 +- scripts/Makefile.gcc-plugins | 16 +------ scripts/Makefile.stackleak | 21 +++++++++ scripts/gcc-plugins/stackleak_plugin.c | 52 ++++++++++----------- Documentation/admin-guide/sysctl/kernel.rst | 2 +- Documentation/security/self-protection.rst | 2 +- arch/x86/entry/calling.h | 4 +- arch/x86/include/asm/init.h | 2 +- include/linux/init.h | 4 +- include/linux/sched.h | 4 +- include/linux/stackleak.h | 6 +-- arch/arm/kernel/entry-common.S | 2 +- arch/arm64/kernel/entry.S | 2 +- arch/riscv/kernel/entry.S | 2 +- arch/s390/kernel/entry.S | 2 +- drivers/misc/lkdtm/stackleak.c | 8 ++-- drivers/nvme/host/pci.c | 2 +- kernel/stackleak.c | 4 +- tools/objtool/check.c | 2 +- tools/testing/selftests/lkdtm/config | 2 +- MAINTAINERS | 6 ++- kernel/configs/hardening.config | 6 +++ 36 files changed, 122 insertions(+), 90 deletions(-) create mode 100644 scripts/Makefile.stackleak
The only reason nvme_pci_npages_prp() could be used as a compile-time known result in BUILD_BUG_ON() is because the compiler was always choosing to inline the function. Under special circumstances (sanitizer coverage functions disabled for __init functions on ARCH=um), the compiler decided to stop inlining it:
drivers/nvme/host/pci.c: In function 'nvme_init': include/linux/compiler_types.h:557:45: error: call to '__compiletime_assert_678' declared with attribute error: BUILD_BUG_ON failed: nvme_pci_npages_prp() > NVME_MAX_NR_ALLOCATIONS 557 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^ include/linux/compiler_types.h:538:25: note: in definition of macro '__compiletime_assert' 538 | prefix ## suffix(); \ | ^~~~~~ include/linux/compiler_types.h:557:9: note: in expansion of macro '_compiletime_assert' 557 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^~~~~~~~~~~~~~~~~~~ include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG' 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) | ^~~~~~~~~~~~~~~~ drivers/nvme/host/pci.c:3804:9: note: in expansion of macro 'BUILD_BUG_ON' 3804 | BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_ALLOCATIONS); | ^~~~~~~~~~~~
Force it to be __always_inline to make sure it is always available for use with BUILD_BUG_ON().
Reported-by: kernel test robot lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202505061846.12FMyRjj-lkp@intel.com/ Fixes: c372cdd1efdf ("nvme-pci: iod npages fits in s8") Signed-off-by: Kees Cook kees@kernel.org --- Cc: Keith Busch kbusch@kernel.org Cc: Jens Axboe axboe@kernel.dk Cc: Christoph Hellwig hch@lst.de Cc: Sagi Grimberg sagi@grimberg.me Cc: linux-nvme@lists.infradead.org --- drivers/nvme/host/pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index b178d52eac1b..9ab070a9f037 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -390,7 +390,7 @@ static bool nvme_dbbuf_update_and_check_event(u16 value, __le32 *dbbuf_db, * as it only leads to a small amount of wasted memory for the lifetime of * the I/O. */ -static int nvme_pci_npages_prp(void) +static __always_inline int nvme_pci_npages_prp(void) { unsigned max_bytes = (NVME_MAX_KB_SZ * 1024) + NVME_CTRL_PAGE_SIZE; unsigned nprps = DIV_ROUND_UP(max_bytes, NVME_CTRL_PAGE_SIZE);
On Wed, May 07, 2025 at 11:16:07AM -0700, Kees Cook wrote:
Force it to be __always_inline to make sure it is always available for use with BUILD_BUG_ON().
Reviewed-by: Keith Busch kbusch@kernel.org
While __noinstr already contained __no_sanitize_coverage, it needs to be added to __init and __head section markings to support the Clang implementation of CONFIG_STACKLEAK. This is to make sure the stack depth tracking callback is not executed in unsupported contexts.
The other sanitizer coverage options (trace-pc and trace-cmp) aren't needed in __head nor __init either ("We are interested in code coverage as a function of a syscall inputs"[1]), so this appears safe to disable for them as well.
Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/... [1] Signed-off-by: Kees Cook kees@kernel.org --- Cc: Marco Elver elver@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: x86@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ard Biesheuvel ardb@kernel.org Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Hou Wenlong houwenlong.hwl@antgroup.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Masahiro Yamada masahiroy@kernel.org Cc: "Peter Zijlstra (Intel)" peterz@infradead.org Cc: Luis Chamberlain mcgrof@kernel.org Cc: Sami Tolvanen samitolvanen@google.com Cc: Arnd Bergmann arnd@arndb.de Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: kasan-dev@googlegroups.com --- arch/x86/include/asm/init.h | 2 +- include/linux/init.h | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h index 8b1b1abcef15..6bfdaeddbae8 100644 --- a/arch/x86/include/asm/init.h +++ b/arch/x86/include/asm/init.h @@ -5,7 +5,7 @@ #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000 #define __head __section(".head.text") __no_sanitize_undefined __no_stack_protector #else -#define __head __section(".head.text") __no_sanitize_undefined +#define __head __section(".head.text") __no_sanitize_undefined __no_sanitize_coverage #endif
struct x86_mapping_info { diff --git a/include/linux/init.h b/include/linux/init.h index ee1309473bc6..c65a050d52a7 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -49,7 +49,9 @@
/* These are for everybody (although not all archs will actually discard it in modules) */ -#define __init __section(".init.text") __cold __latent_entropy __noinitretpoline +#define __init __section(".init.text") __cold __latent_entropy \ + __noinitretpoline \ + __no_sanitize_coverage #define __initdata __section(".init.data") #define __initconst __section(".init.rodata") #define __exitdata __section(".exit.data")
+Cc KCOV maintainers
On Wed, 7 May 2025 at 20:16, Kees Cook kees@kernel.org wrote:
While __noinstr already contained __no_sanitize_coverage, it needs to be added to __init and __head section markings to support the Clang implementation of CONFIG_STACKLEAK. This is to make sure the stack depth tracking callback is not executed in unsupported contexts.
The other sanitizer coverage options (trace-pc and trace-cmp) aren't needed in __head nor __init either ("We are interested in code coverage as a function of a syscall inputs"[1]), so this appears safe to disable for them as well.
@ Dmitry, Aleksandr - Will this produce some unwanted side-effects for syzbot? I also think it's safe, but just double checking.
Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/... [1] Signed-off-by: Kees Cook kees@kernel.org
Acked-by: Marco Elver elver@google.com
Cc: Marco Elver elver@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: x86@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ard Biesheuvel ardb@kernel.org Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Hou Wenlong houwenlong.hwl@antgroup.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Masahiro Yamada masahiroy@kernel.org Cc: "Peter Zijlstra (Intel)" peterz@infradead.org Cc: Luis Chamberlain mcgrof@kernel.org Cc: Sami Tolvanen samitolvanen@google.com Cc: Arnd Bergmann arnd@arndb.de Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: kasan-dev@googlegroups.com
arch/x86/include/asm/init.h | 2 +- include/linux/init.h | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h index 8b1b1abcef15..6bfdaeddbae8 100644 --- a/arch/x86/include/asm/init.h +++ b/arch/x86/include/asm/init.h @@ -5,7 +5,7 @@ #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000 #define __head __section(".head.text") __no_sanitize_undefined __no_stack_protector #else -#define __head __section(".head.text") __no_sanitize_undefined +#define __head __section(".head.text") __no_sanitize_undefined __no_sanitize_coverage #endif
struct x86_mapping_info { diff --git a/include/linux/init.h b/include/linux/init.h index ee1309473bc6..c65a050d52a7 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -49,7 +49,9 @@
/* These are for everybody (although not all archs will actually discard it in modules) */ -#define __init __section(".init.text") __cold __latent_entropy __noinitretpoline +#define __init __section(".init.text") __cold __latent_entropy \
__noinitretpoline \__no_sanitize_coverage#define __initdata __section(".init.data") #define __initconst __section(".init.rodata")
#define __exitdata __section(".exit.data")
2.34.1
On Thu, 8 May 2025 at 14:23, Marco Elver elver@google.com wrote:
+Cc KCOV maintainers
On Wed, 7 May 2025 at 20:16, Kees Cook kees@kernel.org wrote:
While __noinstr already contained __no_sanitize_coverage, it needs to be added to __init and __head section markings to support the Clang implementation of CONFIG_STACKLEAK. This is to make sure the stack depth tracking callback is not executed in unsupported contexts.
The other sanitizer coverage options (trace-pc and trace-cmp) aren't needed in __head nor __init either ("We are interested in code coverage as a function of a syscall inputs"[1]), so this appears safe to disable for them as well.
@ Dmitry, Aleksandr - Will this produce some unwanted side-effects for syzbot? I also think it's safe, but just double checking.
I do not see any problems with this.
Link: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/... [1] Signed-off-by: Kees Cook kees@kernel.org
Acked-by: Marco Elver elver@google.com
Cc: Marco Elver elver@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: x86@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ard Biesheuvel ardb@kernel.org Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Hou Wenlong houwenlong.hwl@antgroup.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Masahiro Yamada masahiroy@kernel.org Cc: "Peter Zijlstra (Intel)" peterz@infradead.org Cc: Luis Chamberlain mcgrof@kernel.org Cc: Sami Tolvanen samitolvanen@google.com Cc: Arnd Bergmann arnd@arndb.de Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: kasan-dev@googlegroups.com
arch/x86/include/asm/init.h | 2 +- include/linux/init.h | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h index 8b1b1abcef15..6bfdaeddbae8 100644 --- a/arch/x86/include/asm/init.h +++ b/arch/x86/include/asm/init.h @@ -5,7 +5,7 @@ #if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000 #define __head __section(".head.text") __no_sanitize_undefined __no_stack_protector #else -#define __head __section(".head.text") __no_sanitize_undefined +#define __head __section(".head.text") __no_sanitize_undefined __no_sanitize_coverage #endif
struct x86_mapping_info { diff --git a/include/linux/init.h b/include/linux/init.h index ee1309473bc6..c65a050d52a7 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -49,7 +49,9 @@
/* These are for everybody (although not all archs will actually discard it in modules) */ -#define __init __section(".init.text") __cold __latent_entropy __noinitretpoline +#define __init __section(".init.text") __cold __latent_entropy \
__noinitretpoline \__no_sanitize_coverage#define __initdata __section(".init.data") #define __initconst __section(".init.rodata")
#define __exitdata __section(".exit.data")
2.34.1
In preparation for adding Clang sanitizer coverage stack depth tracking that can support stack depth callbacks, remove "GCC_PLUGIN" from "CONFIG_GCC_PLUGIN_STACKLEAK" and remove "PLUGIN" from "DISABLE_STACKLEAK_PLUGIN". Rearrange the Kconfig to have a top-level CONFIG_STACKLEAK that will depend on either GCC plugins or Clang soon.
While here, also split "prev_lowest_stack" into CONFIG_STACKLEAK_METRICS, since that's the only place it is referenced from.
Signed-off-by: Kees Cook kees@kernel.org --- Cc: Arnd Bergmann arnd@arndb.de Cc: x86@kernel.org Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: kvmarm@lists.linux.dev Cc: linux-riscv@lists.infradead.org Cc: linux-s390@vger.kernel.org Cc: linux-efi@vger.kernel.org Cc: linux-hardening@vger.kernel.org Cc: linux-kbuild@vger.kernel.org Cc: linux-security-module@vger.kernel.org Cc: linux-kselftest@vger.kernel.org --- security/Kconfig.hardening | 18 +++++++++++------- arch/arm/boot/compressed/Makefile | 2 +- arch/arm64/kernel/pi/Makefile | 2 +- arch/arm64/kvm/hyp/nvhe/Makefile | 2 +- arch/riscv/kernel/pi/Makefile | 2 +- arch/riscv/purgatory/Makefile | 2 +- arch/x86/purgatory/Makefile | 2 +- drivers/firmware/efi/libstub/Makefile | 6 +++--- kernel/Makefile | 4 ++-- lib/Makefile | 2 +- scripts/Makefile.gcc-plugins | 4 ++-- Documentation/admin-guide/sysctl/kernel.rst | 2 +- Documentation/security/self-protection.rst | 2 +- arch/x86/entry/calling.h | 4 ++-- include/linux/sched.h | 4 +++- include/linux/stackleak.h | 4 ++-- arch/arm/kernel/entry-common.S | 2 +- arch/arm64/kernel/entry.S | 2 +- arch/riscv/kernel/entry.S | 2 +- arch/s390/kernel/entry.S | 2 +- drivers/misc/lkdtm/stackleak.c | 8 ++++---- tools/testing/selftests/lkdtm/config | 2 +- 22 files changed, 43 insertions(+), 37 deletions(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index c17366ce8224..2d5852676991 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -158,10 +158,10 @@ config GCC_PLUGIN_STRUCTLEAK_VERBOSE initialized. Since not all existing initializers are detected by the plugin, this can produce false positive warnings.
-config GCC_PLUGIN_STACKLEAK +config STACKLEAK bool "Poison kernel stack before returning from syscalls" - depends on GCC_PLUGINS depends on HAVE_ARCH_STACKLEAK + depends on GCC_PLUGINS help This option makes the kernel erase the kernel stack before returning from system calls. This has the effect of leaving @@ -179,6 +179,10 @@ config GCC_PLUGIN_STACKLEAK are advised to test this feature on your expected workload before deploying it.
+config GCC_PLUGIN_STACKLEAK + def_bool STACKLEAK + depends on GCC_PLUGINS + help This plugin was ported from grsecurity/PaX. More information at: * https://grsecurity.net/ * https://pax.grsecurity.net/ @@ -197,9 +201,9 @@ config STACKLEAK_TRACK_MIN_SIZE int "Minimum stack frame size of functions tracked by STACKLEAK" default 100 range 0 4096 - depends on GCC_PLUGIN_STACKLEAK + depends on STACKLEAK help - The STACKLEAK gcc plugin instruments the kernel code for tracking + The STACKLEAK options instruments the kernel code for tracking the lowest border of the kernel stack (and for some other purposes). It inserts the stackleak_track_stack() call for the functions with a stack frame size greater than or equal to this parameter. @@ -207,7 +211,7 @@ config STACKLEAK_TRACK_MIN_SIZE
config STACKLEAK_METRICS bool "Show STACKLEAK metrics in the /proc file system" - depends on GCC_PLUGIN_STACKLEAK + depends on STACKLEAK depends on PROC_FS help If this is set, STACKLEAK metrics for every task are available in @@ -219,11 +223,11 @@ config STACKLEAK_METRICS
config STACKLEAK_RUNTIME_DISABLE bool "Allow runtime disabling of kernel stack erasing" - depends on GCC_PLUGIN_STACKLEAK + depends on STACKLEAK help This option provides 'stack_erasing' sysctl, which can be used in runtime to control kernel stack erasing for kernels built with - CONFIG_GCC_PLUGIN_STACKLEAK. + CONFIG_STACKLEAK.
config INIT_ON_ALLOC_DEFAULT_ON bool "Enable heap memory zeroing on allocation by default" diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index d61369b1eabe..cc71343694c7 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -9,7 +9,7 @@ OBJS =
HEAD = head.o OBJS += misc.o decompress.o -CFLAGS_decompress.o += $(DISABLE_STACKLEAK_PLUGIN) +CFLAGS_decompress.o += $(DISABLE_STACKLEAK) ifeq ($(CONFIG_DEBUG_UNCOMPRESS),y) OBJS += debug.o AFLAGS_head.o += -DDEBUG diff --git a/arch/arm64/kernel/pi/Makefile b/arch/arm64/kernel/pi/Makefile index 4d11a8c29181..77159298f3c6 100644 --- a/arch/arm64/kernel/pi/Makefile +++ b/arch/arm64/kernel/pi/Makefile @@ -2,7 +2,7 @@ # Copyright 2022 Google LLC
KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \ - -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \ + -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK) \ $(DISABLE_LATENT_ENTROPY_PLUGIN) \ $(call cc-option,-mbranch-protection=none) \ -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile index b43426a493df..4e00a2a8ad0c 100644 --- a/arch/arm64/kvm/hyp/nvhe/Makefile +++ b/arch/arm64/kvm/hyp/nvhe/Makefile @@ -12,7 +12,7 @@ asflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS ccflags-y := -D__KVM_NVHE_HYPERVISOR__ -D__DISABLE_EXPORTS -D__DISABLE_TRACE_MMIO__ ccflags-y += -fno-stack-protector \ -DDISABLE_BRANCH_PROFILING \ - $(DISABLE_STACKLEAK_PLUGIN) + $(DISABLE_STACKLEAK)
hostprogs := gen-hyprel HOST_EXTRACFLAGS += -I$(objtree)/include diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile index 81d69d45c06c..40238ed13ea1 100644 --- a/arch/riscv/kernel/pi/Makefile +++ b/arch/riscv/kernel/pi/Makefile @@ -2,7 +2,7 @@ # This file was copied from arm64/kernel/pi/Makefile.
KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \ - -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \ + -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK) \ $(call cc-option,-mbranch-protection=none) \ -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ -include $(srctree)/include/linux/hidden.h \ diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index fb9c917c9b45..af8fa4aded5c 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -53,7 +53,7 @@ targets += purgatory.ro purgatory.chk
PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel PURGATORY_CFLAGS := -mcmodel=medany -ffreestanding -fno-zero-initialized-in-bss -PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING +PURGATORY_CFLAGS += $(DISABLE_STACKLEAK) -DDISABLE_BRANCH_PROFILING PURGATORY_CFLAGS += -fno-stack-protector -g0
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile index ebdfd7b84feb..5450d5f7fd88 100644 --- a/arch/x86/purgatory/Makefile +++ b/arch/x86/purgatory/Makefile @@ -35,7 +35,7 @@ targets += purgatory.ro purgatory.chk PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel PURGATORY_CFLAGS := -mcmodel=small -ffreestanding -fno-zero-initialized-in-bss -g0 PURGATORY_CFLAGS += -fpic -fvisibility=hidden -PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING +PURGATORY_CFLAGS += $(DISABLE_STACKLEAK) -DDISABLE_BRANCH_PROFILING PURGATORY_CFLAGS += -fno-stack-protector
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index d23a1b9fed75..1cfdde43da02 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -22,15 +22,15 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -std=gnu11 \
# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly # disable the stackleak plugin -cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \ +cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK) \ -fno-unwind-tables -fno-asynchronous-unwind-tables cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \ -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \ -DEFI_HAVE_STRCMP -fno-builtin -fpic \ $(call cc-option,-mno-single-pic-base) \ - $(DISABLE_STACKLEAK_PLUGIN) + $(DISABLE_STACKLEAK) cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \ - $(DISABLE_STACKLEAK_PLUGIN) + $(DISABLE_STACKLEAK) cflags-$(CONFIG_LOONGARCH) += -fpie
cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt diff --git a/kernel/Makefile b/kernel/Makefile index 434929de17ef..79583e3501b4 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -137,8 +137,8 @@ obj-$(CONFIG_WATCH_QUEUE) += watch_queue.o obj-$(CONFIG_RESOURCE_KUNIT_TEST) += resource_kunit.o obj-$(CONFIG_SYSCTL_KUNIT_TEST) += sysctl-test.o
-CFLAGS_stackleak.o += $(DISABLE_STACKLEAK_PLUGIN) -obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o +CFLAGS_stackleak.o += $(DISABLE_STACKLEAK) +obj-$(CONFIG_STACKLEAK) += stackleak.o KASAN_SANITIZE_stackleak.o := n KCSAN_SANITIZE_stackleak.o := n KCOV_INSTRUMENT_stackleak.o := n diff --git a/lib/Makefile b/lib/Makefile index c38582f187dd..190c2eecffbf 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -337,7 +337,7 @@ obj-$(CONFIG_UBSAN) += ubsan.o UBSAN_SANITIZE_ubsan.o := n KASAN_SANITIZE_ubsan.o := n KCSAN_SANITIZE_ubsan.o := n -CFLAGS_ubsan.o := -fno-stack-protector $(DISABLE_STACKLEAK_PLUGIN) +CFLAGS_ubsan.o := -fno-stack-protector $(DISABLE_STACKLEAK)
obj-$(CONFIG_SBITMAP) += sbitmap.o
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index e50dc931be49..33ddf5bfda34 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -32,9 +32,9 @@ gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \ gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) \ += -fplugin-arg-stackleak_plugin-verbose ifdef CONFIG_GCC_PLUGIN_STACKLEAK - DISABLE_STACKLEAK_PLUGIN += -fplugin-arg-stackleak_plugin-disable + DISABLE_STACKLEAK += -fplugin-arg-stackleak_plugin-disable endif -export DISABLE_STACKLEAK_PLUGIN +export DISABLE_STACKLEAK
# All the plugin CFLAGS are collected here in case a build target needs to # filter them out of the KBUILD_CFLAGS. diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index dd49a89a62d3..c94475661a80 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1465,7 +1465,7 @@ stack_erasing =============
This parameter can be used to control kernel stack erasing at the end -of syscalls for kernels built with ``CONFIG_GCC_PLUGIN_STACKLEAK``. +of syscalls for kernels built with ``CONFIG_STACKLEAK``.
That erasing reduces the information which kernel stack leak bugs can reveal and blocks some uninitialized stack variable attacks. diff --git a/Documentation/security/self-protection.rst b/Documentation/security/self-protection.rst index 910668e665cb..67a266d38172 100644 --- a/Documentation/security/self-protection.rst +++ b/Documentation/security/self-protection.rst @@ -303,7 +303,7 @@ Memory poisoning
When releasing memory, it is best to poison the contents, to avoid reuse attacks that rely on the old contents of memory. E.g., clear stack on a -syscall return (``CONFIG_GCC_PLUGIN_STACKLEAK``), wipe heap memory on a +syscall return (``CONFIG_STACKLEAK``), wipe heap memory on a free. This frustrates many uninitialized variable attacks, stack content exposures, heap content exposures, and use-after-free attacks.
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index d83236b96f22..790e63df94a2 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -369,7 +369,7 @@ For 32-bit we have the following conventions - kernel is built with .endm
.macro STACKLEAK_ERASE_NOCLOBBER -#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK PUSH_AND_CLEAR_REGS call stackleak_erase POP_REGS @@ -388,7 +388,7 @@ For 32-bit we have the following conventions - kernel is built with #endif /* !CONFIG_X86_64 */
.macro STACKLEAK_ERASE -#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK call stackleak_erase #endif .endm diff --git a/include/linux/sched.h b/include/linux/sched.h index f96ac1982893..f323a4d9f0ef 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1599,8 +1599,10 @@ struct task_struct { /* Used by BPF for per-TASK xdp storage */ struct bpf_net_context *bpf_net_context;
-#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK unsigned long lowest_stack; +#endif +#ifdef CONFIG_STACKLEAK_METRICS unsigned long prev_lowest_stack; #endif
diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h index 3be2cb564710..71e8242fd8f2 100644 --- a/include/linux/stackleak.h +++ b/include/linux/stackleak.h @@ -12,7 +12,7 @@ #define STACKLEAK_POISON -0xBEEF #define STACKLEAK_SEARCH_DEPTH 128
-#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK #include <asm/stacktrace.h> #include <linux/linkage.h>
@@ -82,7 +82,7 @@ asmlinkage void noinstr stackleak_erase_on_task_stack(void); asmlinkage void noinstr stackleak_erase_off_task_stack(void); void __no_caller_saved_registers noinstr stackleak_track_stack(void);
-#else /* !CONFIG_GCC_PLUGIN_STACKLEAK */ +#else /* !CONFIG_STACKLEAK */ static inline void stackleak_task_init(struct task_struct *t) { } #endif
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index f379c852dcb7..9921898d29a1 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -119,7 +119,7 @@ no_work_pending:
ct_user_enter save = 0
-#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK bl stackleak_erase_on_task_stack #endif restore_user_regs fast = 0, offset = 0 diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 5ae2a34b50bd..c5456ff920d3 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -614,7 +614,7 @@ SYM_CODE_END(ret_to_kernel) SYM_CODE_START_LOCAL(ret_to_user) ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step enable_step_tsk x19, x2 -#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK bl stackleak_erase_on_task_stack #endif kernel_exit 0 diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 33a5a9f2a0d4..d6e9903817f7 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -220,7 +220,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception) #endif bnez s0, 1f
-#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK call stackleak_erase_on_task_stack #endif
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index dd291c9ad6a6..6b43318dc0cc 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -124,7 +124,7 @@ _LPP_OFFSET = __LC_LPP #endif
.macro STACKLEAK_ERASE -#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +#ifdef CONFIG_STACKLEAK brasl %r14,stackleak_erase_on_task_stack #endif .endm diff --git a/drivers/misc/lkdtm/stackleak.c b/drivers/misc/lkdtm/stackleak.c index f1d022160913..ab8c690a039a 100644 --- a/drivers/misc/lkdtm/stackleak.c +++ b/drivers/misc/lkdtm/stackleak.c @@ -11,7 +11,7 @@ #include "lkdtm.h" #include <linux/stackleak.h>
-#if defined(CONFIG_GCC_PLUGIN_STACKLEAK) +#if defined(CONFIG_STACKLEAK) /* * Check that stackleak tracks the lowest stack pointer and erases the stack * below this as expected. @@ -129,16 +129,16 @@ static void lkdtm_STACKLEAK_ERASING(void) check_stackleak_irqoff(); local_irq_restore(flags); } -#else /* defined(CONFIG_GCC_PLUGIN_STACKLEAK) */ +#else /* defined(CONFIG_STACKLEAK) */ static void lkdtm_STACKLEAK_ERASING(void) { if (IS_ENABLED(CONFIG_HAVE_ARCH_STACKLEAK)) { - pr_err("XFAIL: stackleak is not enabled (CONFIG_GCC_PLUGIN_STACKLEAK=n)\n"); + pr_err("XFAIL: stackleak is not enabled (CONFIG_STACKLEAK=n)\n"); } else { pr_err("XFAIL: stackleak is not supported on this arch (HAVE_ARCH_STACKLEAK=n)\n"); } } -#endif /* defined(CONFIG_GCC_PLUGIN_STACKLEAK) */ +#endif /* defined(CONFIG_STACKLEAK) */
static struct crashtype crashtypes[] = { CRASHTYPE(STACKLEAK_ERASING), diff --git a/tools/testing/selftests/lkdtm/config b/tools/testing/selftests/lkdtm/config index 7afe05e8c4d7..b9b1275c07e8 100644 --- a/tools/testing/selftests/lkdtm/config +++ b/tools/testing/selftests/lkdtm/config @@ -2,7 +2,7 @@ CONFIG_LKDTM=y CONFIG_DEBUG_LIST=y CONFIG_SLAB_FREELIST_HARDENED=y CONFIG_FORTIFY_SOURCE=y -CONFIG_GCC_PLUGIN_STACKLEAK=y +CONFIG_STACKLEAK=y CONFIG_HARDENED_USERCOPY=y CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=y CONFIG_INIT_ON_FREE_DEFAULT_ON=y
* Kees Cook kees@kernel.org wrote:
The STACKLEAK gcc plugin instruments the kernel code for tracking
The STACKLEAK options instruments the kernel code for tracking
speling.
Also, any chance to fix this terrible name? Should be something like KSTACKZERO or KSTACKCLEAR, to tell people that it doesn't leak the stack but prevents leaks on the stack by clearing it, and that it's about the kernel stack, not any other stack.
Thanks,
Ingo
On Wed, May 07, 2025 at 08:45:15PM +0200, Ingo Molnar wrote:
- Kees Cook kees@kernel.org wrote:
The STACKLEAK gcc plugin instruments the kernel code for tracking
The STACKLEAK options instruments the kernel code for trackingspeling.
Thanks!
Also, any chance to fix this terrible name? Should be something like KSTACKZERO or KSTACKCLEAR, to tell people that it doesn't leak the stack but prevents leaks on the stack by clearing it, and that it's about the kernel stack, not any other stack.
Yeah, better to name it for what it does rather than want to protects against. The internal naming for what it does is "stack erase", so perhaps KSTACK_ERASE ?
-Kees
* Kees Cook kees@kernel.org wrote:
On Wed, May 07, 2025 at 08:45:15PM +0200, Ingo Molnar wrote:
- Kees Cook kees@kernel.org wrote:
The STACKLEAK gcc plugin instruments the kernel code for tracking
The STACKLEAK options instruments the kernel code for trackingspeling.
Thanks!
Also, any chance to fix this terrible name? Should be something like KSTACKZERO or KSTACKCLEAR, to tell people that it doesn't leak the stack but prevents leaks on the stack by clearing it, and that it's about the kernel stack, not any other stack.
Yeah, better to name it for what it does rather than want to protects against. The internal naming for what it does is "stack erase", so perhaps KSTACK_ERASE ?
That's even better, and I like the word separation as well. Thanks!
Ingo
The Clang stack depth tracking implementation has a fixed name for the stack depth tracking callback, "__sanitizer_cov_stack_depth", so rename the GCC plugin function to match since it has no external dependencies.
Signed-off-by: Kees Cook kees@kernel.org --- Cc: Arnd Bergmann arnd@arndb.de Cc: linux-hardening@vger.kernel.org --- security/Kconfig.hardening | 4 +- scripts/gcc-plugins/stackleak_plugin.c | 52 +++++++++++++------------- include/linux/stackleak.h | 2 +- kernel/stackleak.c | 4 +- tools/objtool/check.c | 2 +- 5 files changed, 32 insertions(+), 32 deletions(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 2d5852676991..2be6aed71c92 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -205,8 +205,8 @@ config STACKLEAK_TRACK_MIN_SIZE help The STACKLEAK options instruments the kernel code for tracking the lowest border of the kernel stack (and for some other purposes). - It inserts the stackleak_track_stack() call for the functions with - a stack frame size greater than or equal to this parameter. + It inserts the __sanitizer_cov_stack_depth() call for the functions + with a stack frame size greater than or equal to this parameter. If unsure, leave the default value 100.
config STACKLEAK_METRICS diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c index d20c47d21ad8..e486488c867d 100644 --- a/scripts/gcc-plugins/stackleak_plugin.c +++ b/scripts/gcc-plugins/stackleak_plugin.c @@ -9,7 +9,7 @@ * any of the gcc libraries * * This gcc plugin is needed for tracking the lowest border of the kernel stack. - * It instruments the kernel code inserting stackleak_track_stack() calls: + * It instruments the kernel code inserting __sanitizer_cov_stack_depth() calls: * - after alloca(); * - for the functions with a stack frame size greater than or equal * to the "track-min-size" plugin parameter. @@ -33,7 +33,7 @@ __visible int plugin_is_GPL_compatible;
static int track_frame_size = -1; static bool build_for_x86 = false; -static const char track_function[] = "stackleak_track_stack"; +static const char track_function[] = "__sanitizer_cov_stack_depth"; static bool disable = false; static bool verbose = false;
@@ -58,7 +58,7 @@ static void add_stack_tracking_gcall(gimple_stmt_iterator *gsi, bool after) cgraph_node_ptr node; basic_block bb;
- /* Insert calling stackleak_track_stack() */ + /* Insert calling __sanitizer_cov_stack_depth() */ stmt = gimple_build_call(track_function_decl, 0); gimple_call = as_a_gcall(stmt); if (after) @@ -120,12 +120,12 @@ static void add_stack_tracking_gasm(gimple_stmt_iterator *gsi, bool after) gcc_assert(build_for_x86);
/* - * Insert calling stackleak_track_stack() in asm: - * asm volatile("call stackleak_track_stack" + * Insert calling __sanitizer_cov_stack_depth() in asm: + * asm volatile("call __sanitizer_cov_stack_depth" * :: "r" (current_stack_pointer)) * Use ASM_CALL_CONSTRAINT trick from arch/x86/include/asm/asm.h. * This constraint is taken into account during gcc shrink-wrapping - * optimization. It is needed to be sure that stackleak_track_stack() + * optimization. It is needed to be sure that __sanitizer_cov_stack_depth() * call is inserted after the prologue of the containing function, * when the stack frame is prepared. */ @@ -137,7 +137,7 @@ static void add_stack_tracking_gasm(gimple_stmt_iterator *gsi, bool after) input = build_tree_list(NULL_TREE, build_const_char_string(2, "r")); input = chainon(NULL_TREE, build_tree_list(input, sp_decl)); vec_safe_push(inputs, input); - asm_call = gimple_build_asm_vec("call stackleak_track_stack", + asm_call = gimple_build_asm_vec("call __sanitizer_cov_stack_depth", inputs, NULL, NULL, NULL); gimple_asm_set_volatile(asm_call, true); if (after) @@ -151,11 +151,11 @@ static void add_stack_tracking(gimple_stmt_iterator *gsi, bool after) { /* * The 'no_caller_saved_registers' attribute is used for - * stackleak_track_stack(). If the compiler supports this attribute for - * the target arch, we can add calling stackleak_track_stack() in asm. + * __sanitizer_cov_stack_depth(). If the compiler supports this attribute for + * the target arch, we can add calling __sanitizer_cov_stack_depth() in asm. * That improves performance: we avoid useless operations with the * caller-saved registers in the functions from which we will remove - * stackleak_track_stack() call during the stackleak_cleanup pass. + * __sanitizer_cov_stack_depth() call during the stackleak_cleanup pass. */ if (lookup_attribute_spec(get_identifier("no_caller_saved_registers"))) add_stack_tracking_gasm(gsi, after); @@ -165,7 +165,7 @@ static void add_stack_tracking(gimple_stmt_iterator *gsi, bool after)
/* * Work with the GIMPLE representation of the code. Insert the - * stackleak_track_stack() call after alloca() and into the beginning + * __sanitizer_cov_stack_depth() call after alloca() and into the beginning * of the function if it is not instrumented. */ static unsigned int stackleak_instrument_execute(void) @@ -205,7 +205,7 @@ static unsigned int stackleak_instrument_execute(void) DECL_NAME_POINTER(current_function_decl)); }
- /* Insert stackleak_track_stack() call after alloca() */ + /* Insert __sanitizer_cov_stack_depth() call after alloca() */ add_stack_tracking(&gsi, true); if (bb == entry_bb) prologue_instrumented = true; @@ -241,7 +241,7 @@ static unsigned int stackleak_instrument_execute(void) return 0; }
- /* Insert stackleak_track_stack() call at the function beginning */ + /* Insert __sanitizer_cov_stack_depth() call at the function beginning */ bb = entry_bb; if (!single_pred_p(bb)) { /* gcc_assert(bb_loop_depth(bb) || @@ -270,15 +270,15 @@ static void remove_stack_tracking_gcall(void) rtx_insn *insn, *next;
/* - * Find stackleak_track_stack() calls. Loop through the chain of insns, + * Find __sanitizer_cov_stack_depth() calls. Loop through the chain of insns, * which is an RTL representation of the code for a function. * * The example of a matching insn: - * (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack") - * [flags 0x41] <function_decl 0x7f7cd3302a80 stackleak_track_stack>) - * [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list - * (symbol_ref ("stackleak_track_stack") [flags 0x41] <function_decl - * 0x7f7cd3302a80 stackleak_track_stack>) (expr_list (0) (nil))) (nil)) + * (call_insn 8 4 10 2 (call (mem (symbol_ref ("__sanitizer_cov_stack_depth") + * [flags 0x41] <function_decl 0x7f7cd3302a80 __sanitizer_cov_stack_depth>) + * [0 __sanitizer_cov_stack_depth S1 A8]) (0)) 675 {*call} (expr_list + * (symbol_ref ("__sanitizer_cov_stack_depth") [flags 0x41] <function_decl + * 0x7f7cd3302a80 __sanitizer_cov_stack_depth>) (expr_list (0) (nil))) (nil)) */ for (insn = get_insns(); insn; insn = next) { rtx body; @@ -318,7 +318,7 @@ static void remove_stack_tracking_gcall(void) if (SYMBOL_REF_DECL(body) != track_function_decl) continue;
- /* Delete the stackleak_track_stack() call */ + /* Delete the __sanitizer_cov_stack_depth() call */ delete_insn_and_edges(insn); #if BUILDING_GCC_VERSION < 8000 if (GET_CODE(next) == NOTE && @@ -340,12 +340,12 @@ static bool remove_stack_tracking_gasm(void) gcc_assert(build_for_x86);
/* - * Find stackleak_track_stack() asm calls. Loop through the chain of + * Find __sanitizer_cov_stack_depth() asm calls. Loop through the chain of * insns, which is an RTL representation of the code for a function. * * The example of a matching insn: * (insn 11 5 12 2 (parallel [ (asm_operands/v - * ("call stackleak_track_stack") ("") 0 + * ("call __sanitizer_cov_stack_depth") ("") 0 * [ (reg/v:DI 7 sp [ current_stack_pointer ]) ] * [ (asm_input:DI ("r")) ] []) * (clobber (reg:CC 17 flags)) ]) -1 (nil)) @@ -375,7 +375,7 @@ static bool remove_stack_tracking_gasm(void) continue;
if (strcmp(ASM_OPERANDS_TEMPLATE(body), - "call stackleak_track_stack")) { + "call __sanitizer_cov_stack_depth")) { continue; }
@@ -389,7 +389,7 @@ static bool remove_stack_tracking_gasm(void)
/* * Work with the RTL representation of the code. - * Remove the unneeded stackleak_track_stack() calls from the functions + * Remove the unneeded __sanitizer_cov_stack_depth() calls from the functions * which don't call alloca() and don't have a large enough stack frame size. */ static unsigned int stackleak_cleanup_execute(void) @@ -474,13 +474,13 @@ static bool stackleak_gate(void) return track_frame_size >= 0; }
-/* Build the function declaration for stackleak_track_stack() */ +/* Build the function declaration for __sanitizer_cov_stack_depth() */ static void stackleak_start_unit(void *gcc_data __unused, void *user_data __unused) { tree fntype;
- /* void stackleak_track_stack(void) */ + /* void __sanitizer_cov_stack_depth(void) */ fntype = build_function_type_list(void_type_node, NULL_TREE); track_function_decl = build_fn_decl(track_function, fntype); DECL_ASSEMBLER_NAME(track_function_decl); /* for LTO */ diff --git a/include/linux/stackleak.h b/include/linux/stackleak.h index 71e8242fd8f2..a669574a3562 100644 --- a/include/linux/stackleak.h +++ b/include/linux/stackleak.h @@ -80,7 +80,7 @@ static inline void stackleak_task_init(struct task_struct *t) asmlinkage void noinstr stackleak_erase(void); asmlinkage void noinstr stackleak_erase_on_task_stack(void); asmlinkage void noinstr stackleak_erase_off_task_stack(void); -void __no_caller_saved_registers noinstr stackleak_track_stack(void); +void __no_caller_saved_registers noinstr __sanitizer_cov_stack_depth(void);
#else /* !CONFIG_STACKLEAK */ static inline void stackleak_task_init(struct task_struct *t) { } diff --git a/kernel/stackleak.c b/kernel/stackleak.c index bb65321761b4..5158468968e2 100644 --- a/kernel/stackleak.c +++ b/kernel/stackleak.c @@ -156,7 +156,7 @@ asmlinkage void noinstr stackleak_erase_off_task_stack(void) __stackleak_erase(false); }
-void __used __no_caller_saved_registers noinstr stackleak_track_stack(void) +void __used __no_caller_saved_registers noinstr __sanitizer_cov_stack_depth(void) { unsigned long sp = current_stack_pointer;
@@ -174,4 +174,4 @@ void __used __no_caller_saved_registers noinstr stackleak_track_stack(void) current->lowest_stack = sp; } } -EXPORT_SYMBOL(stackleak_track_stack); +EXPORT_SYMBOL(__sanitizer_cov_stack_depth); diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 3a411064fa34..05d0095c1384 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1191,7 +1191,7 @@ static const char *uaccess_safe_builtin[] = { "__ubsan_handle_shift_out_of_bounds", "__ubsan_handle_load_invalid_value", /* STACKLEAK */ - "stackleak_track_stack", + "__sanitizer_cov_stack_depth", /* TRACE_BRANCH_PROFILING */ "ftrace_likely_update", /* STACKPROTECTOR */
In preparation for Clang stack depth tracking for stackleak, split the stackleak-specific cflags out of GCC_PLUGINS_CFLAGS into STACKLEAK_CFLAGS.
Signed-off-by: Kees Cook kees@kernel.org --- Cc: Arnd Bergmann arnd@arndb.de Cc: x86@kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: sparclinux@vger.kernel.org Cc: linux-kbuild@vger.kernel.org Cc: linux-hardening@vger.kernel.org --- Makefile | 1 + arch/arm/vdso/Makefile | 2 +- arch/arm64/kernel/vdso/Makefile | 3 ++- arch/sparc/vdso/Makefile | 3 ++- arch/x86/entry/vdso/Makefile | 3 ++- scripts/Makefile.gcc-plugins | 16 ++-------------- scripts/Makefile.stackleak | 15 +++++++++++++++ MAINTAINERS | 6 ++++-- 8 files changed, 29 insertions(+), 20 deletions(-) create mode 100644 scripts/Makefile.stackleak
diff --git a/Makefile b/Makefile index 5aa9ee52a765..1af8dfbcf0af 100644 --- a/Makefile +++ b/Makefile @@ -1089,6 +1089,7 @@ include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct +include-$(CONFIG_STACKLEAK) += scripts/Makefile.stackleak include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile index cb044bfd145d..f05a27909a76 100644 --- a/arch/arm/vdso/Makefile +++ b/arch/arm/vdso/Makefile @@ -26,7 +26,7 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH) CFLAGS_REMOVE_vdso.o = -pg
# Force -O2 to avoid libgcc dependencies -CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) +CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(RANDSTRUCT_CFLAGS) $(STACKLEAK_CFLAGS) $(GCC_PLUGINS_CFLAGS) ifeq ($(c-gettimeofday-y),) CFLAGS_vgettimeofday.o = -O2 else diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile index 5e27e46aa496..d4f60027f910 100644 --- a/arch/arm64/kernel/vdso/Makefile +++ b/arch/arm64/kernel/vdso/Makefile @@ -36,7 +36,8 @@ ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO # -Wmissing-prototypes and -Wmissing-declarations are removed from # the CFLAGS to make possible to build the kernel with CONFIG_WERROR enabled. CC_FLAGS_REMOVE_VDSO := $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \ - $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) \ + $(RANDSTRUCT_CFLAGS) $(STACKLEAK_CFLAGS) \ + $(GCC_PLUGINS_CFLAGS) \ $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \ -Wmissing-prototypes -Wmissing-declarations
diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile index fdc4a8f5a49c..d0cfaa2f508a 100644 --- a/arch/sparc/vdso/Makefile +++ b/arch/sparc/vdso/Makefile @@ -48,7 +48,7 @@ CFL := $(PROFILING) -mcmodel=medlow -fPIC -O2 -fasynchronous-unwind-tables -m64
SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7)
-$(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) +$(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(STACKLEAK_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
# # vDSO code runs in userspace and -pg doesn't help with profiling anyway. @@ -79,6 +79,7 @@ KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS)) KBUILD_CFLAGS_32 := $(filter-out -mcmodel=medlow,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32)) +KBUILD_CFLAGS_32 := $(filter-out $(STACKLEAK_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 += -m32 -msoft-float -fpic diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index 54d3e9774d62..9e912b6a889c 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -62,7 +62,7 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),) endif endif
-$(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) +$(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(STACKLEAK_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL) $(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO
# @@ -123,6 +123,7 @@ KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32)) +KBUILD_CFLAGS_32 := $(filter-out $(STACKLEAK_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32)) KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32)) diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 33ddf5bfda34..e27ffe8e7c75 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -22,20 +22,6 @@ export DISABLE_STRUCTLEAK_PLUGIN gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) \ += -DSTRUCTLEAK_PLUGIN
-gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak_plugin.so -gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \ - += -DSTACKLEAK_PLUGIN -gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \ - += -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE) -gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \ - += -fplugin-arg-stackleak_plugin-arch=$(SRCARCH) -gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) \ - += -fplugin-arg-stackleak_plugin-verbose -ifdef CONFIG_GCC_PLUGIN_STACKLEAK - DISABLE_STACKLEAK += -fplugin-arg-stackleak_plugin-disable -endif -export DISABLE_STACKLEAK - # All the plugin CFLAGS are collected here in case a build target needs to # filter them out of the KBUILD_CFLAGS. GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) -DGCC_PLUGINS @@ -50,6 +36,8 @@ gcc-plugin-external-$(CONFIG_GCC_PLUGIN_SANCOV) \ += sancov_plugin.so gcc-plugin-external-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) \ += randomize_layout_plugin.so +gcc-plugin-external-$(CONFIG_GCC_PLUGIN_STACKLEAK) \ + += stackleak_plugin.so
# All enabled GCC plugins are collected here for building in # scripts/gcc-scripts/Makefile. diff --git a/scripts/Makefile.stackleak b/scripts/Makefile.stackleak new file mode 100644 index 000000000000..1db0835b29d4 --- /dev/null +++ b/scripts/Makefile.stackleak @@ -0,0 +1,15 @@ +# SPDX-License-Identifier: GPL-2.0 + +ifdef CONFIG_GCC_PLUGIN_STACKLEAK +stackleak-cflags-y += -fplugin=$(objtree)/scripts/gcc-plugins/stackleak_plugin.so +stackleak-cflags-y += -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE) +stackleak-cflags-y += -fplugin-arg-stackleak_plugin-arch=$(SRCARCH) +stackleak-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) += -fplugin-arg-stackleak_plugin-verbose +DISABLE_STACKLEAK := -fplugin-arg-stackleak_plugin-disable +endif + +STACKLEAK_CFLAGS := $(stackleak-cflags-y) + +export STACKLEAK_CFLAGS DISABLE_STACKLEAK + +KBUILD_CFLAGS += $(STACKLEAK_CFLAGS) diff --git a/MAINTAINERS b/MAINTAINERS index dc535c67a745..9a2be2dd96c9 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9827,8 +9827,6 @@ L: linux-hardening@vger.kernel.org S: Maintained T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening F: Documentation/kbuild/gcc-plugins.rst -F: include/linux/stackleak.h -F: kernel/stackleak.c F: scripts/Makefile.gcc-plugins F: scripts/gcc-plugins/
@@ -12890,11 +12888,15 @@ F: Documentation/ABI/testing/sysfs-kernel-warn_count F: arch/*/configs/hardening.config F: include/linux/overflow.h F: include/linux/randomize_kstack.h +F: include/linux/stackleak.h F: include/linux/ucopysize.h F: kernel/configs/hardening.config +F: kernel/stackleak.c F: lib/tests/randstruct_kunit.c F: lib/tests/usercopy_kunit.c F: mm/usercopy.c +F: scripts/Makefile.randstruct +F: scripts/Makefile.stackleak F: security/Kconfig.hardening K: \b(add|choose)_random_kstack_offset\b K: \b__check_(object_size|heap_object)\b
Wire up CONFIG_STACKLEAK to Clang 21's new stack depth tracking callback[1] option.
Link: https://clang.llvm.org/docs/SanitizerCoverage.html#tracing-stack-depth [1] Signed-off-by: Kees Cook kees@kernel.org --- Cc: Arnd Bergmann arnd@arndb.de Cc: Masahiro Yamada masahiroy@kernel.org Cc: Nathan Chancellor nathan@kernel.org Cc: Nicolas Schier nicolas.schier@linux.dev Cc: Marco Elver elver@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Ard Biesheuvel ardb@kernel.org Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: linux-kbuild@vger.kernel.org Cc: kasan-dev@googlegroups.com Cc: linux-hardening@vger.kernel.org --- security/Kconfig.hardening | 5 ++++- scripts/Makefile.stackleak | 6 ++++++ 2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 2be6aed71c92..94aa8612c4e4 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -158,10 +158,13 @@ config GCC_PLUGIN_STRUCTLEAK_VERBOSE initialized. Since not all existing initializers are detected by the plugin, this can produce false positive warnings.
+config CC_HAS_SANCOV_STACK_DEPTH_CALLBACK + def_bool $(cc-option,-fsanitize-coverage-stack-depth-callback-min=1) + config STACKLEAK bool "Poison kernel stack before returning from syscalls" depends on HAVE_ARCH_STACKLEAK - depends on GCC_PLUGINS + depends on GCC_PLUGINS || CC_HAS_SANCOV_STACK_DEPTH_CALLBACK help This option makes the kernel erase the kernel stack before returning from system calls. This has the effect of leaving diff --git a/scripts/Makefile.stackleak b/scripts/Makefile.stackleak index 1db0835b29d4..639cc32bcd1d 100644 --- a/scripts/Makefile.stackleak +++ b/scripts/Makefile.stackleak @@ -8,6 +8,12 @@ stackleak-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) += -fplugin-arg-stacklea DISABLE_STACKLEAK := -fplugin-arg-stackleak_plugin-disable endif
+ifdef CONFIG_CC_IS_CLANG +stackleak-cflags-y += -fsanitize-coverage=stack-depth +stackleak-cflags-y += -fsanitize-coverage-stack-depth-callback-min=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE) +DISABLE_STACKLEAK := -fno-sanitize-coverage=stack-depth +endif + STACKLEAK_CFLAGS := $(stackleak-cflags-y)
export STACKLEAK_CFLAGS DISABLE_STACKLEAK
Since we can wipe the stack with both Clang and GCC plugins, enable this for the "hardening.config" for wider testing.
Signed-off-by: Kees Cook kees@kernel.org --- Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: linux-hardening@vger.kernel.org --- kernel/configs/hardening.config | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/configs/hardening.config b/kernel/configs/hardening.config index dd7c32fb5ac1..3da00926b4eb 100644 --- a/kernel/configs/hardening.config +++ b/kernel/configs/hardening.config @@ -63,6 +63,9 @@ CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y # Initialize all stack variables to zero on function entry. CONFIG_INIT_STACK_ALL_ZERO=y
+# Wipe kernel stack after syscall completion to reduce stale data lifetime. +CONFIG_STACKLEAK=y + # Wipe RAM at reboot via EFI. For more details, see: # https://trustedcomputinggroup.org/resource/pc-client-work-group-platform-res... # https://bugzilla.redhat.com/show_bug.cgi?id=1532058
To reduce stale data lifetimes, enable CONFIG_INIT_ON_FREE_DEFAULT_ON as well. This matches the addition of CONFIG_STACKLEAK=y, which is doing similar for stack memory.
Signed-off-by: Kees Cook kees@kernel.org --- Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: linux-hardening@vger.kernel.org --- kernel/configs/hardening.config | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/configs/hardening.config b/kernel/configs/hardening.config index 3da00926b4eb..7d92a740e490 100644 --- a/kernel/configs/hardening.config +++ b/kernel/configs/hardening.config @@ -60,6 +60,9 @@ CONFIG_LIST_HARDENED=y # Initialize all heap variables to zero on allocation. CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
+# Initialize all heap variables to zero on free to reduce stale data lifetime. +CONFIG_INIT_ON_FREE_DEFAULT_ON=y + # Initialize all stack variables to zero on function entry. CONFIG_INIT_STACK_ALL_ZERO=y
linux-kselftest-mirror@lists.linaro.org
-
Dmitry Vyukov -
Ingo Molnar -
Kees Cook -
Keith Busch -
Marco Elver