From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 27 Jan 2019 04:58:00 +0000 (+0000)
Subject: btrfs: fix potential oops in device_list_add
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=92900e5160a5444d47dd376bc40066b709fbb5a6;p=openwrt%2Fstaging%2Fblogic.git

btrfs: fix potential oops in device_list_add

alloc_fs_devices() can return ERR_PTR(-ENOMEM), so dereferencing its
result before the check for IS_ERR() is a bad idea.

Fixes: d1a63002829a4 ("btrfs: add members to fs_devices to track fsid changes")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3e4f8f88353e..15561926ab32 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -957,11 +957,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 		else
 			fs_devices = alloc_fs_devices(disk_super->fsid, NULL);
 
-		fs_devices->fsid_change = fsid_change_in_progress;
-
 		if (IS_ERR(fs_devices))
 			return ERR_CAST(fs_devices);
 
+		fs_devices->fsid_change = fsid_change_in_progress;
+
 		mutex_lock(&fs_devices->device_list_mutex);
 		list_add(&fs_devices->fs_list, &fs_uuids);