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>
diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index d30d67c..591be0e 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -66,8 +66,8 @@
 	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 @@
 
 	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 @@
 	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 @@
 		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)