x86/microcode/AMD: Track patch allocation size explicitly

BugLink: https://bugs.launchpad.net/bugs/1996825
[ 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@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/
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h
index fcbfe94903bb8bb86c55ecfcc1749621c01c9c0f..d130d21f4862de62b34cff093cfd0621cac397d0 100644 (file)
--- 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 3d4a48336084fdb1d0247f3cf88850be2e75c150..5a16844b99d33c934c1291ee9b43d16a4671c155 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -782,6 +782,7 @@ 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;
@@ -863,7 +864,7 @@ 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;
 }