Re: net/packet: use-after-free in packet_rcv_fanout

[Eric Dumazet]

On Fri, 2017-02-10 at 09:59 -0800, Eric Dumazet wrote:
> On Fri, 2017-02-10 at 09:49 -0800, Cong Wang wrote:
> > On Thu, Feb 9, 2017 at 7:23 PM, Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> > > On Thu, 2017-02-09 at 19:19 -0800, Eric Dumazet wrote:
> > >
> > >> More likely the bug is in fanout_add(), with a buggy sequence in error
> > >> case, and not correct locking.
> > >>
> > >> kfree(po->rollover);
> > >> po->rollover = NULL;
> > >>
> > >> Two cpus entering fanout_add() (using the same af_packet socket,
> > >> syzkaller courtesy...) might both see po->fanout being NULL.
> > >>
> > >> Then they grab the mutex.  Too late...
> > >
> > > Patch could be :
> > >
> > 
> > For me, clearly the data structure that use-after-free'd is struct sock
> > rather than struct packet_rollover.
> 
> Fine. But your patch makes absolutely no sense.

At least, Anoob patch is making a step into the right direction ;)

https://patchwork.ozlabs.org/patch/726532/