Merge branch 'stable/for-jens-3.13-take-two' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip into for-linus

drivers/block/xen-blkfront.c

@@ -489,7 +489,7 @@ static int blkif_queue_request(struct request *req)
 
 			if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
 			    (i % SEGS_PER_INDIRECT_FRAME == 0)) {
-				unsigned long pfn;
+				unsigned long uninitialized_var(pfn);
 
 				if (segments)
 					kunmap_atomic(segments);
@@ -2011,6 +2011,10 @@ static void blkif_release(struct gendisk *disk, fmode_t mode)
 
 	bdev = bdget_disk(disk, 0);
 
+	if (!bdev) {
+		WARN(1, "Block device %s yanked out from us!\n", disk->disk_name);
+		goto out_mutex;
+	}
 	if (bdev->bd_openers)
 		goto out;
 
@@ -2041,6 +2045,7 @@ static void blkif_release(struct gendisk *disk, fmode_t mode)
 
 out:
 	bdput(bdev);
+out_mutex:
 	mutex_unlock(&blkfront_mutex);
 }