Re: [PATCH] btrfs: fix memory leak of fs_devices in degraded seed device path

[David Sterba]

On Wed, Dec 10, 2025 at 06:58:07PM +0530, Deepanshu Kartikey wrote:
> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=eadd98df8bceb15d7fed
> Tested-by: syzbot+eadd98df8bceb15d7fed@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>

Reviewed-by: David Sterba <dsterba@xxxxxxxx>