[PATCH 6.12 004/567] btrfs: fix memory leak of fs_devices in degraded seed device path

Greg Kroah-Hartman
2026-01-06T17:16:02Z

From: Deepanshu Kartikey <kartikey406@gmail.com>

[ Upstream commit b57f2ddd28737db6ff0e9da8467f0ab9d707e997 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/volumes.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index ce991a8390466..9c6e96f630132 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7071,6 +7071,7 @@ 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;
}

--
2.51.0