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| author |   Kees Cook <keescook@chromium.org> | 2023-10-18 10:53:58 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2023-10-18 17:56:32 -0700 |
| commit | 0e108725f6cc5b3be9e607f89c9fbcbb236367b7 (patch) | |
| tree | 149102c39237fe844793971015c83202d0c9f699 /include/linux/string.h | |
| parent | hardening: x86: drop reference to removed config AMD_IOMMU_V2 (diff) | |
| download | wireguard-linux-0e108725f6cc5b3be9e607f89c9fbcbb236367b7.tar.xz wireguard-linux-0e108725f6cc5b3be9e607f89c9fbcbb236367b7.zip | |
string: Adjust strtomem() logic to allow for smaller sources
Arnd noticed we have a case where a shorter source string is being copied
into a destination byte array, but this results in a strnlen() call that
exceeds the size of the source. This is seen with -Wstringop-overread:
In file included from ../include/linux/uuid.h:11,
from ../include/linux/mod_devicetable.h:14,
from ../include/linux/cpufeature.h:12,
from ../arch/x86/coco/tdx/tdx.c:7:
../arch/x86/coco/tdx/tdx.c: In function 'tdx_panic.constprop':
../include/linux/string.h:284:9: error: 'strnlen' specified bound 64 exceeds source size 60 [-Werror=stringop-overread]
284 | memcpy_and_pad(dest, _dest_len, src, strnlen(src, _dest_len), pad); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../arch/x86/coco/tdx/tdx.c:124:9: note: in expansion of macro 'strtomem_pad'
124 | strtomem_pad(message.str, msg, '\0');
| ^~~~~~~~~~~~
Use the smaller of the two buffer sizes when calling strnlen(). When
src length is unknown (SIZE_MAX), it is adjusted to use dest length,
which is what the original code did.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Fixes: dfbafa70bde2 ("string: Introduce strtomem() and strtomem_pad()")
Tested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'include/linux/string.h')
| -rw-r--r-- | include/linux/string.h | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/string.h b/include/linux/string.h index dbfc66400050..9e3cb6923b0e 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -277,10 +277,12 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count, */ #define strtomem_pad(dest, src, pad) do { \ const size_t _dest_len = __builtin_object_size(dest, 1); \ + const size_t _src_len = __builtin_object_size(src, 1); \ \ BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ _dest_len == (size_t)-1); \ - memcpy_and_pad(dest, _dest_len, src, strnlen(src, _dest_len), pad); \ + memcpy_and_pad(dest, _dest_len, src, \ + strnlen(src, min(_src_len, _dest_len)), pad); \ } while (0) /** @@ -298,10 +300,11 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count, */ #define strtomem(dest, src) do { \ const size_t _dest_len = __builtin_object_size(dest, 1); \ + const size_t _src_len = __builtin_object_size(src, 1); \ \ BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ _dest_len == (size_t)-1); \ - memcpy(dest, src, min(_dest_len, strnlen(src, _dest_len))); \ + memcpy(dest, src, strnlen(src, min(_src_len, _dest_len))); \ } while (0) /** |