Patch "x86/microcode/AMD: Track patch allocation size explicitly" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    x86/microcode/AMD: Track patch allocation size explicitly

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-microcode-amd-track-patch-allocation-size-explic.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 601ef622e8422f03e1551f7b392215b55d1f9f94
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date:   Wed Sep 21 20:10:10 2022 -0700

    x86/microcode/AMD: Track patch allocation size explicitly
    
    [ Upstream commit 712f210a457d9c32414df246a72781550bc23ef6 ]
    
    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: 757885e94a22 ("x86, microcode, amd: Early microcode patch loading support for AMD")
    Suggested-by: Daniel Micay <danielmicay@xxxxxxxxx>
    Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Signed-off-by: Borislav Petkov <bp@xxxxxxx>
    Link: https://lore.kernel.org/lkml/CA+DvKQ+bp7Y7gmaVhacjv9uF6Ar-o4tet872h4Q8RPYPJjcJQA@xxxxxxxxxxxxxx/
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h
index 91a06cef50c1..f73327397b89 100644
--- a/arch/x86/include/asm/microcode.h
+++ b/arch/x86/include/asm/microcode.h
@@ -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;
 };
diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index 3f6b137ef4e6..c87936441339 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -783,6 +783,7 @@ 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;
@@ -864,7 +865,7 @@ 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;
 }