x86/microcode/AMD: Add microcode container verification

Add container and patch verification functions to the AMD microcode update driver. These functions check whether a passed buffer contains the relevant structure, whether it isn't truncated and (for actual microcode patches) whether the size of a patch is not too large for a particular CPU family. By adding these checks as separate functions the actual microcode loading code won't get interspersed with a lot of checks and so will be more readable. [ bp: Make all pr_err() calls into pr_debug() and drop the verify_patch() bits. ] Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: x86-ml <x86@kernel.org> Link: http://lkml.kernel.org/r/3014e96c82cd90761b4601bd2cfe59c4119e46a7.1529424596.git.mail@maciej.szmigiero.name
2018-06-19 20:47:32 +02:00 · 2018-06-19 20:47:32 +02:00 · f4ff25916c
parent 479229d160
commit f4ff25916c
1 changed files with 101 additions and 0 deletions
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@ -73,6 +73,107 @@ static u16 find_equiv_id(struct equiv_cpu_entry *equiv_table, u32 sig)
 	return 0;
 }

+/*
+ * Check whether there is a valid microcode container file at the beginning
+ * of @buf of size @buf_size. Set @early to use this function in the early path.
+ */
+static bool verify_container(const u8 *buf, size_t buf_size, bool early)
+{
+	u32 cont_magic;
+
+	if (buf_size <= CONTAINER_HDR_SZ) {
+		if (!early)
+			pr_debug("Truncated microcode container header.\n");
+
+		return false;
+	}
+
+	cont_magic = *(const u32 *)buf;
+	if (cont_magic != UCODE_MAGIC) {
+		if (!early)
+			pr_debug("Invalid magic value (0x%08x).\n", cont_magic);
+
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Check whether there is a valid, non-truncated CPU equivalence table at the
+ * beginning of @buf of size @buf_size. Set @early to use this function in the
+ * early path.
+ */
+static bool verify_equivalence_table(const u8 *buf, size_t buf_size, bool early)
+{
+	const u32 *hdr = (const u32 *)buf;
+	u32 cont_type, equiv_tbl_len;
+
+	if (!verify_container(buf, buf_size, early))
+		return false;
+
+	cont_type = hdr[1];
+	if (cont_type != UCODE_EQUIV_CPU_TABLE_TYPE) {
+		if (!early)
+			pr_debug("Wrong microcode container equivalence table type: %u.\n",
+			       cont_type);
+
+		return false;
+	}
+
+	buf_size -= CONTAINER_HDR_SZ;
+
+	equiv_tbl_len = hdr[2];
+	if (equiv_tbl_len < sizeof(struct equiv_cpu_entry) ||
+	    buf_size < equiv_tbl_len) {
+		if (!early)
+			pr_debug("Truncated equivalence table.\n");
+
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Check whether there is a valid, non-truncated microcode patch section at the
+ * beginning of @buf of size @buf_size. Set @early to use this function in the
+ * early path.
+ */
+static bool verify_patch_section(const u8 *buf, size_t buf_size, bool early)
+{
+	const u32 *hdr;
+	u32 patch_type, patch_size;
+
+	if (buf_size < SECTION_HDR_SIZE) {
+		if (!early)
+			pr_debug("Truncated patch section.\n");
+
+		return false;
+	}
+
+	hdr = (const u32 *)buf;
+	patch_type = hdr[0];
+	patch_size = hdr[1];
+
+	if (patch_type != UCODE_UCODE_TYPE) {
+		if (!early)
+			pr_debug("Invalid type field (0x%x) in container file section header.\n",
+				patch_type);
+
+		return false;
+	}
+
+	if (patch_size < sizeof(struct microcode_header_amd)) {
+		if (!early)
+			pr_debug("Patch of size %u too short.\n", patch_size);
+
+		return false;
+	}
+
+	return true;
+}
+
 /*
 * This scans the ucode blob for the proper container as we can have multiple
 * containers glued together. Returns the equivalence ID from the equivalence