4.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nikolay Borisov <nborisov@xxxxxxxx>
commit fd649f10c3d21ee9d7542c609f29978bdf73ab94 upstream.
Commit 4fde46f0cc71 ("Btrfs: free the stale device") introduced
btrfs_free_stale_device which iterates the device lists for all
registered btrfs filesystems and deletes those devices which aren't
mounted. In a btrfs_devices structure has only 1 device attached to it
and it is unused then btrfs_free_stale_devices will proceed to also free
the btrfs_fs_devices struct itself. Currently this leads to a use after
free since list_for_each_entry will try to perform a check on the
already freed memory to see if it has to terminate the loop.
The fix is to use 'break' when we know we are freeing the current
fs_devs.
Fixes: 4fde46f0cc71 ("Btrfs: free the stale device")
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/volumes.c | 1 +
1 file changed, 1 insertion(+)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -574,6 +574,7 @@ static void btrfs_free_stale_device(stru
btrfs_sysfs_remove_fsid(fs_devs);
list_del(&fs_devs->list);
free_fs_devices(fs_devs);
+ break;
} else {
fs_devs->num_devices--;
list_del(&dev->dev_list);