kexec: avoid freeing NULL pointer in image_crash_alloc()

Though there is no error if we free a NULL pointer, I think we could
avoid this behaviour.  Change the code a little in kimage_crash_alloc()
could avoid this kind of unnecessary free.
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kexec.c

@@ -316,7 +316,7 @@ static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,
 		mend = mstart + image->segment[i].memsz - 1;
 		/* Ensure we are within the crash kernel limits */
 		if ((mstart < crashk_res.start) || (mend > crashk_res.end))
-			goto out;
+			goto out_free;
 	}
 
 	/*
@@ -329,16 +329,15 @@ static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,
 					   get_order(KEXEC_CONTROL_PAGE_SIZE));
 	if (!image->control_code_page) {
 		printk(KERN_ERR "Could not allocate control_code_buffer\n");
-		goto out;
+		goto out_free;
 	}
 
-	result = 0;
-out:
-	if (result == 0)
-		*rimage = image;
-	else
-		kfree(image);
+	*rimage = image;
+	return 0;
 
+out_free:
+	kfree(image);
+out:
 	return result;
 }