bcache: properly initialize 'path' and 'err' in register_bcache()

[ Upstream commit 29cda39 ]

Patch "bcache: rework error unwinding in register_bcache" from
Christoph Hellwig changes the local variables 'path' and 'err'
in undefined initial state. If the code in register_bcache() jumps
to label 'out:' or 'out_module_put:' by goto, these two variables
might be reference with undefined value by the following line,

	out_module_put:
	        module_put(THIS_MODULE);
	out:
	        pr_info("error %s: %s", path, err);
	        return ret;

Therefore this patch initializes these two local variables properly
in register_bcache() to avoid such issue.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/md/bcache/super.c

@@ -2373,18 +2373,20 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
 			       const char *buffer, size_t size)
 {
 	const char *err;
-	char *path;
+	char *path = NULL;
 	struct cache_sb *sb;
 	struct block_device *bdev = NULL;
 	struct page *sb_page;
 	ssize_t ret;
 
 	ret = -EBUSY;
+	err = "failed to reference bcache module";
 	if (!try_module_get(THIS_MODULE))
 		goto out;
 
 	/* For latest state of bcache_is_reboot */
 	smp_mb();
+	err = "bcache is in reboot";
 	if (bcache_is_reboot)
 		goto out_module_put;