x86/microcode/intel: Do the mc_saved_src NULL check first

... and only then deref it. Also, shorten some variable names and rename
others so as to diminish the ubiquitous presence of the "mc_" prefix
everywhere and make it a bit more readable.

Use kcalloc so that we don't kfree() uninitialized memory on the unwind
path, as suggested by Quentin.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>

arch/x86/kernel/cpu/microcode/intel_early.c

@@ -203,7 +203,7 @@ save_microcode(struct mc_saved_data *mc_saved_data,
 	       unsigned int mc_saved_count)
 {
 	int i, j;
-	struct microcode_intel **mc_saved_p;
+	struct microcode_intel **saved_ptr;
 	int ret;
 
 	if (!mc_saved_count)
@@ -212,39 +212,45 @@ save_microcode(struct mc_saved_data *mc_saved_data,
 	/*
 	 * Copy new microcode data.
 	 */
-	mc_saved_p = kmalloc(mc_saved_count*sizeof(struct microcode_intel *),
-			     GFP_KERNEL);
-	if (!mc_saved_p)
+	saved_ptr = kcalloc(mc_saved_count, sizeof(struct microcode_intel *), GFP_KERNEL);
+	if (!saved_ptr)
 		return -ENOMEM;
 
 	for (i = 0; i < mc_saved_count; i++) {
-		struct microcode_intel *mc = mc_saved_src[i];
-		struct microcode_header_intel *mc_header = &mc->hdr;
-		unsigned long mc_size = get_totalsize(mc_header);
-		mc_saved_p[i] = kmalloc(mc_size, GFP_KERNEL);
-		if (!mc_saved_p[i]) {
-			ret = -ENOMEM;
-			goto err;
-		}
+		struct microcode_header_intel *mc_hdr;
+		struct microcode_intel *mc;
+		unsigned long size;
+
 		if (!mc_saved_src[i]) {
 			ret = -EINVAL;
 			goto err;
 		}
-		memcpy(mc_saved_p[i], mc, mc_size);
+
+		mc     = mc_saved_src[i];
+		mc_hdr = &mc->hdr;
+		size   = get_totalsize(mc_hdr);
+
+		saved_ptr[i] = kmalloc(size, GFP_KERNEL);
+		if (!saved_ptr[i]) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		memcpy(saved_ptr[i], mc, size);
 	}
 
 	/*
 	 * Point to newly saved microcode.
 	 */
-	mc_saved_data->mc_saved = mc_saved_p;
+	mc_saved_data->mc_saved = saved_ptr;
 	mc_saved_data->mc_saved_count = mc_saved_count;
 
 	return 0;
 
 err:
 	for (j = 0; j <= i; j++)
-		kfree(mc_saved_p[j]);
-	kfree(mc_saved_p);
+		kfree(saved_ptr[j]);
+	kfree(saved_ptr);
 
 	return ret;
 }