# Re: \[PATCH net\] packet: unconditionally free po-\>rollover

- From: David Miller \<davem@davemloft.net\>
- Date: 2019-06-03 01:11:32 
- List: netdev
- Page: https://ratatoskr.run/netdev/2019/06/11136887
- Thread: https://ratatoskr.run/netdev/2019/05/11136647/t.md

```text
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Fri, 31 May 2019 12:37:23 -0400

> From: Willem de Bruijn <willemb@google.com>
> 
> Rollover used to use a complex RCU mechanism for assignment, which had
> a race condition. The below patch fixed the bug and greatly simplified
> the logic.
> 
> The feature depends on fanout, but the state is private to the socket.
> Fanout_release returns f only when the last member leaves and the
> fanout struct is to be freed.
> 
> Destroy rollover unconditionally, regardless of fanout state.
> 
> Fixes: 57f015f5eccf2 ("packet: fix crash in fanout_demux_rollover()")
> Reported-by: syzbot <redacted>
> Diagnosed-by: Dmitry Vyukov [ref]
> Signed-off-by: Willem de Bruijn <willemb@google.com>

Applied and queued up for -stable.
```