4.9-stable review patch. If anyone has any objections, please let me know.
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From: Nikolay Borisov nborisov@suse.com
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@suse.com Reviewed-by: Anand Jain anand.jain@oracle.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/volumes.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -583,6 +583,7 @@ void btrfs_free_stale_device(struct btrf 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);