# Re: \[PATCH net\] packet: fix race condition in packet\_set\_ring

- From: David Miller \<davem@davemloft.net\>
- Date: 2016-12-02 17:17:17 
- List: netdev
- Page: https://ratatoskr.run/netdev/2016/12/11036991
- Thread: https://ratatoskr.run/netdev/2016/11/11036711/t.md

```text
From: Eric Dumazet <redacted>
Date: Wed, 30 Nov 2016 14:55:36 -0800

> From: Philip Pettersson <redacted>
> 
> When packet_set_ring creates a ring buffer it will initialize a
> struct timer_list if the packet version is TPACKET_V3. This value
> can then be raced by a different thread calling setsockopt to
> set the version to TPACKET_V1 before packet_set_ring has finished.
> 
> This leads to a use-after-free on a function pointer in the
> struct timer_list when the socket is closed as the previously
> initialized timer will not be deleted.
> 
> The bug is fixed by taking lock_sock(sk) in packet_setsockopt when
> changing the packet version while also taking the lock at the start
> of packet_set_ring.
> 
> Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
> Signed-off-by: Philip Pettersson <redacted>
> Signed-off-by: Eric Dumazet <redacted>

Applied and queued up for -stable, thanks.
```