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

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

[Deepanshu Kartikey]

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
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/btrfs/volumes.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index ae1742a35e76..13c514684cfb 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7128,6 +7128,7 @@ 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;
 	}
 
-- 
2.43.0

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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=eadd98df8bceb15d7fed
> Tested-by: syzbot+eadd98df8bceb15d7fed@syzkaller.appspotmail.com
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>

Reviewed-by: David Sterba <dsterba@suse.com>

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

[Qu Wenruo]

在 2025/12/10 23:58, Deepanshu Kartikey 写道:
> 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
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
>   fs/btrfs/volumes.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index ae1742a35e76..13c514684cfb 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -7128,6 +7128,7 @@ 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;
>   	}
>