btrfs: fix memory leak of fs_devices in degraded seed device path

In open_seed_devices(), when find_fsid() fails and we're in DEGRADED
mode, a new fs_devices is allocated via alloc_fs_devices() but is never
added to the seed_list before returning. This contrasts with the normal
path where fs_devices is properly added via list_add().

If any error occurs later in read_one_dev() or btrfs_read_chunk_tree(),
the cleanup code iterates seed_list to free seed devices, but this
orphaned fs_devices is never found and never freed, causing a memory
leak. Any devices allocated via add_missing_dev() and attached to this
fs_devices are also leaked.

Fix this by adding the newly allocated fs_devices to seed_list in the
degraded path, consistent with the normal path.

Fixes: 5f37583569442 ("Btrfs: move the missing device to its own fs device list")
Reported-by: syzbot+eadd98df8bceb15d7fed@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=eadd98df8bceb15d7fed
Tested-by: syzbot+eadd98df8bceb15d7fed@syzkaller.appspotmail.com
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
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 e81c8ac0d8ae646fee70affe51f0d76f35585b74..e35872149e2facf3c6f9e4c6a8a9948de5e59fda 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7131,6 +7131,7 @@ static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
 
                fs_devices->seeding = true;
                fs_devices->opened = 1;
+               list_add(&fs_devices->seed_list, &fs_info->fs_devices->seed_list);
                return fs_devices;
        }