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| author | Kees Cook <keescook@chromium.org> | 2022-09-20 00:53:13 +0200 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2023-01-05 21:08:29 +0100 |
| commit | 439a1bcac648fe9b59210cde8991fb2acf37bdab (patch) | |
| tree | 89f6e3cef476af5c3bb3e194b804e55217d29602 | |
| parent | rxrpc: replace zero-lenth array with DECLARE_FLEX_ARRAY() helper (diff) | |
| download | linux-439a1bcac648fe9b59210cde8991fb2acf37bdab.tar.xz linux-439a1bcac648fe9b59210cde8991fb2acf37bdab.zip | |
fortify: Use __builtin_dynamic_object_size() when available
Since the commits starting with c37495d6254c ("slab: add __alloc_size
attributes for better bounds checking"), the compilers have runtime
allocation size hints available in some places. This was immediately
available to CONFIG_UBSAN_BOUNDS, but CONFIG_FORTIFY_SOURCE needed
updating to explicitly make use of the hints via the associated
__builtin_dynamic_object_size() helper. Detect and use the builtin when
it is available, increasing the accuracy of the mitigation. When runtime
sizes are not available, __builtin_dynamic_object_size() falls back to
__builtin_object_size(), leaving the existing bounds checking unchanged.
Additionally update the VMALLOC_LINEAR_OVERFLOW LKDTM test to make the
hint invisible, otherwise the architectural defense is not exercised
(the buffer overflow is detected in the memset() rather than when it
crosses the edge of the allocation).
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Tom Rix <trix@redhat.com>
Cc: linux-hardening@vger.kernel.org
Cc: llvm@lists.linux.dev
Reviewed-by: Miguel Ojeda <ojeda@kernel.org> # include/linux/compiler_attributes.h
Signed-off-by: Kees Cook <keescook@chromium.org>
| -rw-r--r-- | drivers/misc/lkdtm/heap.c | 1 | ||||
| -rw-r--r-- | include/linux/compiler_attributes.h | 5 | ||||
| -rw-r--r-- | include/linux/fortify-string.h | 7 |
3 files changed, 13 insertions, 0 deletions
diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c index 62516078a619..0ce4cbf6abda 100644 --- a/drivers/misc/lkdtm/heap.c +++ b/drivers/misc/lkdtm/heap.c @@ -31,6 +31,7 @@ static void lkdtm_VMALLOC_LINEAR_OVERFLOW(void) char *one, *two; one = vzalloc(PAGE_SIZE); + OPTIMIZER_HIDE_VAR(one); two = vzalloc(PAGE_SIZE); pr_info("Attempting vmalloc linear overflow ...\n"); diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 898b3458b24a..56467f86a27c 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -297,6 +297,11 @@ * * clang: https://clang.llvm.org/docs/AttributeReference.html#pass-object-size-pass-dynamic-object-size */ +#if __has_attribute(__pass_dynamic_object_size__) +# define __pass_dynamic_object_size(type) __attribute__((__pass_dynamic_object_size__(type))) +#else +# define __pass_dynamic_object_size(type) +#endif #if __has_attribute(__pass_object_size__) # define __pass_object_size(type) __attribute__((__pass_object_size__(type))) #else diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index 7cad8bb031e9..c9de1f59ee80 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -90,10 +90,17 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) * size, rather than struct size), but there remain some stragglers using * type 0 that will be converted in the future. */ +#if __has_builtin(__builtin_dynamic_object_size) +#define POS __pass_dynamic_object_size(1) +#define POS0 __pass_dynamic_object_size(0) +#define __struct_size(p) __builtin_dynamic_object_size(p, 0) +#define __member_size(p) __builtin_dynamic_object_size(p, 1) +#else #define POS __pass_object_size(1) #define POS0 __pass_object_size(0) #define __struct_size(p) __builtin_object_size(p, 0) #define __member_size(p) __builtin_object_size(p, 1) +#endif #define __compiletime_lessthan(bounds, length) ( \ __builtin_constant_p((bounds) < (length)) && \ |