x86, microcode, AMD: Fix section header size check

The ucode size check has to take the section header size into account
too when sanity checking the section length. Shorten and clarify define
names, while at it.

Caught-by: Ben Hutchings <ben@decadent.org.uk>
Link: http://lkml.kernel.org/r/1302752223.5282.674.camel@localhost
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

arch/x86/kernel/microcode_amd.c

@@ -66,8 +66,8 @@ struct microcode_amd {
 	unsigned int			mpb[0];
 };
 
-#define UCODE_CONTAINER_SECTION_HDR	8
-#define UCODE_CONTAINER_HEADER_SIZE	12
+#define SECTION_HDR_SIZE	8
+#define CONTAINER_HDR_SZ	12
 
 static struct equiv_cpu_entry *equiv_cpu_table;
 
@@ -177,7 +177,7 @@ static unsigned int verify_ucode_size(int cpu, const u8 *buf, unsigned int size)
 
 	actual_size = *(u32 *)(buf + 4);
 
-	if (actual_size > size || actual_size > max_size) {
+	if (actual_size + SECTION_HDR_SIZE > size || actual_size > max_size) {
 		pr_err("section size mismatch\n");
 		return 0;
 	}
@@ -204,8 +204,8 @@ get_next_ucode(int cpu, const u8 *buf, unsigned int size, unsigned int *mc_size)
 	if (!mc)
 		goto out;
 
-	get_ucode_data(mc, buf + UCODE_CONTAINER_SECTION_HDR, actual_size);
-	*mc_size = actual_size + UCODE_CONTAINER_SECTION_HDR;
+	get_ucode_data(mc, buf + SECTION_HDR_SIZE, actual_size);
+	*mc_size = actual_size + SECTION_HDR_SIZE;
 
 out:
 	return mc;
@@ -229,9 +229,10 @@ static int install_equiv_cpu_table(const u8 *buf)
 		return -ENOMEM;
 	}
 
-	get_ucode_data(equiv_cpu_table, buf + UCODE_CONTAINER_HEADER_SIZE, size);
+	get_ucode_data(equiv_cpu_table, buf + CONTAINER_HDR_SZ, size);
 
-	return size + UCODE_CONTAINER_HEADER_SIZE; /* add header length */
+	/* add header length */
+	return size + CONTAINER_HDR_SZ;
 }
 
 static void free_equiv_cpu_table(void)