From 36bf50d7697be18c6bfd0401e037df10bff1e573 Mon Sep 17 00:00:00 2001
From: Andreas Herrmann <andreas.herrmann3@amd.com>
Date: Tue, 31 Jul 2012 15:41:45 +0200
Subject: x86, microcode, AMD: Fix broken ucode patch size check
This issue was recently observed on an AMD C-50 CPU where a patch of
maximum size was applied.
Commit be62adb49294 ("x86, microcode, AMD: Simplify ucode verification")
added current_size in get_matching_microcode(). This is calculated as
size of the ucode patch + 8 (ie. size of the header). Later this is
compared against the maximum possible ucode patch size for a CPU family.
And of course this fails if the patch has already maximum size.
Cc: <stable@vger.kernel.org> [3.3+]
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1344361461-10076-1-git-send-email-bp@amd64.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/kernel/microcode_amd.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index 8a2ce8fd41c0..82746f942cd8 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -143,11 +143,12 @@ static int get_matching_microcode(int cpu, const u8 *ucode_ptr,
unsigned int *current_size)
{
struct microcode_header_amd *mc_hdr;
- unsigned int actual_size;
+ unsigned int actual_size, patch_size;
u16 equiv_cpu_id;
/* size of the current patch we're staring at */
- *current_size = *(u32 *)(ucode_ptr + 4) + SECTION_HDR_SIZE;
+ patch_size = *(u32 *)(ucode_ptr + 4);
+ *current_size = patch_size + SECTION_HDR_SIZE;
equiv_cpu_id = find_equiv_id();
if (!equiv_cpu_id)
@@ -174,7 +175,7 @@ static int get_matching_microcode(int cpu, const u8 *ucode_ptr,
/*
* now that the header looks sane, verify its size
*/
- actual_size = verify_ucode_size(cpu, *current_size, leftover_size);
+ actual_size = verify_ucode_size(cpu, patch_size, leftover_size);
if (!actual_size)
return 0;
--
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