block/rnbd-clt: Fix possible memleak

stable inclusion
from stable-5.10.4
commit 1b75aea3e360f5e660612b6c25a54cb16c313b23
bugzilla: 46903

--------------------------------

[ Upstream commit 46067844 ]

In error case, we do not free the memory for blk_symlink_name.

Do it by free the memory in error case, and set to NULL
afterwards.

Also fix the condition in rnbd_clt_remove_dev_symlink.

Fixes: 64e8a6ec ("block/rnbd-clt: Dynamically alloc buffer for pathname & blk_symlink_name")
Signed-off-by: NJack Wang <jinpu.wang@cloud.ionos.com>
Reviewed-by: NMd Haris Iqbal <haris.iqbal@cloud.ionos.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/block/rnbd/rnbd-clt-sysfs.c

@@ -433,7 +433,7 @@ void rnbd_clt_remove_dev_symlink(struct rnbd_clt_dev *dev)
 	 * i.e. rnbd_clt_unmap_dev_store() leading to a sysfs warning because
 	 * of sysfs link already was removed already.
 	 */
-	if (strlen(dev->blk_symlink_name) && try_module_get(THIS_MODULE)) {
+	if (dev->blk_symlink_name && try_module_get(THIS_MODULE)) {
 		sysfs_remove_link(rnbd_devs_kobj, dev->blk_symlink_name);
 		kfree(dev->blk_symlink_name);
 		module_put(THIS_MODULE);
@@ -516,7 +516,8 @@ static int rnbd_clt_add_dev_symlink(struct rnbd_clt_dev *dev)
 	return 0;
 
 out_err:
-	dev->blk_symlink_name[0] = '\0';
+	kfree(dev->blk_symlink_name);
+	dev->blk_symlink_name = NULL ;
 	return ret;
 }