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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-12-17 08:45:40 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-12-17 08:45:40 -0800 |
| commit | 1f13c38a854d13acafe6feedaa2705e61f79a538 (patch) | |
| tree | 2e7fc9212f7ca10964582e2e02811d3f96bc1af7 | |
| parent | 59dbb9d81adfe07a6f8483269146b407cf9d44d7 (diff) | |
| parent | 239d87327dcd361b0098038995f8908f3296864f (diff) | |
| download | lwn-1f13c38a854d13acafe6feedaa2705e61f79a538.tar.gz lwn-1f13c38a854d13acafe6feedaa2705e61f79a538.zip | |
Merge tag 'hardening-v6.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull hardening fix from Kees Cook:
"Silence a GCC value-range warning that is being ironically triggered
by bounds checking"
* tag 'hardening-v6.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
fortify: Hide run-time copy size from value range tracking
| -rw-r--r-- | include/linux/fortify-string.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index 0d99bf11d260..e4ce1cae03bf 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -616,6 +616,12 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, return false; } +/* + * To work around what seems to be an optimizer bug, the macro arguments + * need to have const copies or the values end up changed by the time they + * reach fortify_warn_once(). See commit 6f7630b1b5bc ("fortify: Capture + * __bos() results in const temp vars") for more details. + */ #define __fortify_memcpy_chk(p, q, size, p_size, q_size, \ p_size_field, q_size_field, op) ({ \ const size_t __fortify_size = (size_t)(size); \ @@ -623,6 +629,8 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, const size_t __q_size = (q_size); \ const size_t __p_size_field = (p_size_field); \ const size_t __q_size_field = (q_size_field); \ + /* Keep a mutable version of the size for the final copy. */ \ + size_t __copy_size = __fortify_size; \ fortify_warn_once(fortify_memcpy_chk(__fortify_size, __p_size, \ __q_size, __p_size_field, \ __q_size_field, FORTIFY_FUNC_ ##op), \ @@ -630,7 +638,11 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size, __fortify_size, \ "field \"" #p "\" at " FILE_LINE, \ __p_size_field); \ - __underlying_##op(p, q, __fortify_size); \ + /* Hide only the run-time size from value range tracking to */ \ + /* silence compile-time false positive bounds warnings. */ \ + if (!__builtin_constant_p(__copy_size)) \ + OPTIMIZER_HIDE_VAR(__copy_size); \ + __underlying_##op(p, q, __copy_size); \ }) /* |