[SRU v2][F/gke][PATCH] net/packet: rx_owner_map depends on pg_vec

[Khalid Elmously]

On 2022-01-27 10:14:29 , Stefan Bader wrote:
> On 27.01.22 09:00, Khalid Elmously wrote:
> > From: Willem de Bruijn <willemb at google.com>
> > 
> > BugLink: https://bugs.launchpad.net/bugs/1959173
> > 
> > Packet sockets may switch ring versions. Avoid misinterpreting state
> > between versions, whose fields share a union. rx_owner_map is only
> > allocated with a packet ring (pg_vec) and both are swapped together.
> > If pg_vec is NULL, meaning no packet ring was allocated, then neither
> > was rx_owner_map. And the field may be old state from a tpacket_v3.
> > 
> > Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
> > Reported-by: Syzbot <syzbot+1ac0994a0a0c55151121 at syzkaller.appspotmail.com>
> > Signed-off-by: Willem de Bruijn <willemb at google.com>
> > Reviewed-by: Eric Dumazet <edumazet at google.com>
> > Link: https://lore.kernel.org/r/20211215143937.106178-1-willemdebruijn.kernel@gmail.com
> > Signed-off-by: Jakub Kicinski <kuba at kernel.org>
> > (cherry picked from commit ec6af094ea28f0f2dda1a6a33b14cd57e36a9755)
> > Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
> > ---
> 
> Would this not better be a change for all relevant distro kernels?

Yes. It is ready to be applied via linux-stable updates for all the main kernels, so they should all get it next cycle, which would mean a release around end of Feb.

However, GKE thinks the risk is high enough that they would strongly prefer it be fixed as soon as possible, so I intend to respin the GKE kernels with this fix as soon as it is applied.


> 
> -Stefan
> 
> >   net/packet/af_packet.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> > index 46943a18a10d..76c2dca7f0a5 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -4492,9 +4492,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
> >   	}
> >   out_free_pg_vec:
> > -	bitmap_free(rx_owner_map);
> > -	if (pg_vec)
> > +	if (pg_vec) {
> > +		bitmap_free(rx_owner_map);
> >   		free_pg_vec(pg_vec, order, req->tp_block_nr);
> > +	}
> >   out:
> >   	return err;
> >   }
>