linux-kernel - [PATCH v3 5/9] x86/microcode/AMD: check patch size in verify_and_add

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Date:   Tue, 13 Mar 2018 22:06:54 +0100
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 5/9] x86/microcode/AMD: check patch size in
 verify_and_add_patch()

Now that we have the PATCH_MAX_SIZE macro correctly computed we can verify
properly the indicated size of a patch in a microcode container file and
whether this file is actually large enough to contain it in the late loader
verify_and_add_patch() function.

The early loader already does the PATCH_MAX_SIZE check in parse_container()
function.

Signed-off-by: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
---
 arch/x86/kernel/cpu/microcode/amd.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index b9f6c06bdc16..0f78200f2f6c 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -485,7 +485,7 @@ static int collect_cpu_info_amd(int cpu, struct cpu_signature *csig)
 }
 
 static unsigned int verify_patch_size(u8 family, u32 patch_size,
-				      unsigned int size)
+				      size_t size)
 {
 	u32 max_size;
 
@@ -507,7 +507,7 @@ static unsigned int verify_patch_size(u8 family, u32 patch_size,
 		break;
 	}
 
-	if (patch_size > min_t(u32, size, max_size)) {
+	if (patch_size > min_t(size_t, size, max_size)) {
 		pr_err("patch size mismatch\n");
 		return 0;
 	}
@@ -616,7 +616,7 @@ static void cleanup(void)
  * driver cannot continue functioning normally. In such cases, we tear
  * down everything we've used up so far and exit.
  */
-static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover)
+static int verify_and_add_patch(u8 family, u8 *fw, size_t leftover)
 {
 	struct microcode_header_amd *mc_hdr;
 	struct ucode_patch *patch;
@@ -624,7 +624,15 @@ static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover)
 	u32 proc_fam;
 	u16 proc_id;
 
+	if (leftover < SECTION_HDR_SIZE + sizeof(*mc_hdr))
+		return leftover;
+
 	patch_size  = *(u32 *)(fw + 4);
+	if (patch_size > PATCH_MAX_SIZE) {
+		pr_err("patch size %u too large\n", patch_size);
+		return -EINVAL;
+	}
+
 	crnt_size   = patch_size + SECTION_HDR_SIZE;
 	mc_hdr	    = (struct microcode_header_amd *)(fw + SECTION_HDR_SIZE);
 	proc_id	    = mc_hdr->processor_rev_id;