linux-kernel - [PATCH v5 3/6] x86/microcode/AMD: Check microcode container data in the early loader

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Date:   Mon, 23 Apr 2018 23:34:08 +0200
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 v5 3/6] x86/microcode/AMD: Check microcode container data in the early loader

This commit converts the early loader in the AMD microcode update driver to
use the container data checking functions introduced by the previous
commit.

We have to be careful to call these functions with 'early' parameter set,
so they won't try to print errors as the early loader runs too early for
printk()-style functions to work.

Signed-off-by: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
---
 arch/x86/kernel/cpu/microcode/amd.c | 45 ++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index 4fafaf0852d7..94fcd702a67a 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -216,29 +216,33 @@ static bool verify_patch(u8 family, const u8 *buf, size_t buf_size, bool early)
  * Returns the amount of bytes consumed while scanning. @desc contains all the
  * data we're going to use in later stages of the application.
  */
-static ssize_t parse_container(u8 *ucode, ssize_t size, struct cont_desc *desc)
+static size_t parse_container(u8 *ucode, size_t size, struct cont_desc *desc)
 {
 	struct equiv_cpu_entry *eq;
-	ssize_t orig_size = size;
+	size_t orig_size = size;
 	u32 *hdr = (u32 *)ucode;
+	u32 equiv_tbl_len;
 	u16 eq_id;
 	u8 *buf;
 
-	/* Am I looking at an equivalence table header? */
-	if (hdr[0] != UCODE_MAGIC ||
-	    hdr[1] != UCODE_EQUIV_CPU_TABLE_TYPE ||
-	    hdr[2] == 0)
+	if (!verify_container(ucode, size, true))
+		return 0;
+
+	if (!verify_equivalence_table(ucode, size, true))
 		return CONTAINER_HDR_SZ;
 
 	buf = ucode;
 
+	equiv_tbl_len = hdr[2];
 	eq = (struct equiv_cpu_entry *)(buf + CONTAINER_HDR_SZ);
 
 	/* Find the equivalence ID of our CPU in this table: */
 	eq_id = find_equiv_id(eq, desc->cpuid_1_eax);
 
-	buf  += hdr[2] + CONTAINER_HDR_SZ;
-	size -= hdr[2] + CONTAINER_HDR_SZ;
+	buf  += CONTAINER_HDR_SZ;
+	buf  += equiv_tbl_len;
+	size -= CONTAINER_HDR_SZ;
+	size -= equiv_tbl_len;
 
 	/*
 	 * Scan through the rest of the container to find where it ends. We do
@@ -250,25 +254,22 @@ static ssize_t parse_container(u8 *ucode, ssize_t size, struct cont_desc *desc)
 
 		hdr = (u32 *)buf;
 
-		if (hdr[0] != UCODE_UCODE_TYPE)
+		if (!verify_patch_section(buf, size, true))
 			break;
 
-		/* Sanity-check patch size. */
 		patch_size = hdr[1];
-		if (patch_size > PATCH_MAX_SIZE)
-			break;
 
-		/* Skip patch section header: */
-		buf  += SECTION_HDR_SIZE;
-		size -= SECTION_HDR_SIZE;
-
-		mc = (struct microcode_amd *)buf;
-		if (eq_id == mc->hdr.processor_rev_id) {
+		mc = (struct microcode_amd *)(buf + SECTION_HDR_SIZE);
+		if (eq_id == mc->hdr.processor_rev_id &&
+		    verify_patch(x86_family(desc->cpuid_1_eax), buf, size,
+				 true)) {
 			desc->psize = patch_size;
 			desc->mc = mc;
 		}
 
+		buf  += SECTION_HDR_SIZE;
 		buf  += patch_size;
+		size -= SECTION_HDR_SIZE;
 		size -= patch_size;
 	}
 
@@ -295,15 +296,13 @@ static ssize_t parse_container(u8 *ucode, ssize_t size, struct cont_desc *desc)
  */
 static void scan_containers(u8 *ucode, size_t size, struct cont_desc *desc)
 {
-	ssize_t rem = size;
-
-	while (rem >= 0) {
-		ssize_t s = parse_container(ucode, rem, desc);
+	while (size > 0) {
+		size_t s = parse_container(ucode, size, desc);
 		if (!s)
 			return;
 
 		ucode += s;
-		rem   -= s;
+		size  -= s;
 	}
 }