From: Daniel Borkmann <dan...@iogearbox.net> Date: Mon, 21 Aug 2017 01:48:12 +0200
> In the current code, dev_map_free() can still race with > dev_map_notification(). > In dev_map_free(), we remove dtab from the list of dtabs after we purged > all entries from it. However, we don't do xchg() with NULL or the like, > so the entry at that point is still pointing to the device. If a unregister > notification comes in at the same time, we therefore risk a double-free, > since the pointer is still present in the map, and then pushed again to > __dev_map_entry_free(). > > All this is completely unnecessary. Just remove the dtab from the list > right before the synchronize_rcu(), so all outstanding readers from the > notifier list have finished by then, thus we don't need to deal with this > corner case anymore and also wouldn't need to nullify dev entires. This is > fine because we iterate over the map releasing all entries and therefore > dev references anyway. > > Fixes: 4cc7b9544b9a ("bpf: devmap fix mutex in rcu critical section") > Signed-off-by: Daniel Borkmann <dan...@iogearbox.net> Applied, thanks Daniel.