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x86/microcode/AMD: Track patch allocation size explicitly

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In preparation for reducing the use of ksize(), record the actual
allocation size for later memcpy(). This avoids copying extra
(uninitialized!) bytes into the patch buffer when the requested
allocation size isn't exactly the size of a kmalloc bucket.
Additionally, fix potential future issues where runtime bounds checking
will notice that the buffer was allocated to a smaller value than
returned by ksize().

Fixes: 757885e94a ("x86, microcode, amd: Early microcode patch loading support for AMD")
Suggested-by: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/lkml/CA+DvKQ+bp7Y7gmaVhacjv9uF6Ar-o4tet872h4Q8RPYPJjcJQA@mail.gmail.com/
This commit is contained in:
Kees Cook 2022-09-21 20:10:10 -07:00 committed by Borislav Petkov
parent 7fce8d6ecc
commit 712f210a45
2 changed files with 3 additions and 1 deletions
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1
arch/x86/include/asm/microcode.h
View File

@ -9,6 +9,7 @@
struct ucode_patch {
struct list_head plist;
void *data; /* Intel uses only this one */
unsigned int size;
u32 patch_id;
u16 equiv_cpu;
};

3
arch/x86/kernel/cpu/microcode/amd.c
View File

@ -788,6 +788,7 @@ static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover,
kfree(patch);
return -EINVAL;
}
patch->size = *patch_size;
mc_hdr = (struct microcode_header_amd *)(fw + SECTION_HDR_SIZE);
proc_id = mc_hdr->processor_rev_id;
@ -869,7 +870,7 @@ load_microcode_amd(bool save, u8 family, const u8 *data, size_t size)
return ret;
memset(amd_ucode_patch, 0, PATCH_MAX_SIZE);
memcpy(amd_ucode_patch, p->data, min_t(u32, ksize(p->data), PATCH_MAX_SIZE));
memcpy(amd_ucode_patch, p->data, min_t(u32, p->size, PATCH_MAX_SIZE));
return ret;
}