RE: af_packet: use after free in prb_retire_rx_blk_timer_expired

[liujian (CE)]

Hi Wang cong,

After apply the patch, I did not hit the issue again.
Thank you~


Best Regards,
liujian

> -----Original Message-----
> From: Dingtianhong
> Sent: Monday, July 24, 2017 9:29 AM
> To: Cong Wang; liujian (CE)
> Cc: Willem de Bruijn; Dave Jones; alexander.levin@xxxxxxxxxxx;
> davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; willemb@xxxxxxxxxx;
> daniel@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: af_packet: use after free in prb_retire_rx_blk_timer_expired
> 
> 
> 
> On 2017/7/24 9:09, Ding Tianhong wrote:
> >
> >
> > On 2017/7/24 1:03, Cong Wang wrote:
> >> On Sun, Jul 23, 2017 at 5:48 AM, liujian (CE) <liujian56@xxxxxxxxxx> wrote:
> >>> Hi
> >>>
> >>> I find it caused by below steps:
> >>> 1. set tp_version to TPACKET_V3 and req->tp_block_nr to 1 2. set
> >>> tp_block_nr to 0 Then pg_vec was freed, and we did not delete the
> >>> timer?
> >>
> >> Thanks for testing!
> >>
> >> Ah, I overlook the initialization case in my previous patch.
> >>
> >> How about the following one? Does it cover all the cases?
> >>
> >>
> >> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index
> >> 008bb34ee324..0615c2a950fa 100644
> >> --- a/net/packet/af_packet.c
> >> +++ b/net/packet/af_packet.c
> >> @@ -4329,7 +4329,7 @@ static int packet_set_ring(struct sock *sk,
> >> union tpacket_req_u *req_u,
> >>                 register_prot_hook(sk);
> >>         }
> >>         spin_unlock(&po->bind_lock);
> >> -       if (closing && (po->tp_version > TPACKET_V2)) {
> >> +       if (pg_vec && (po->tp_version > TPACKET_V2)) {
> >>                 /* Because we don't support block-based V3 on tx-ring
> */
> >>                 if (!tx_ring)
> >>                         prb_shutdown_retire_blk_timer(po,
> rb_queue);
> >>
> >> .
> >
> > Hi, Cong:
> >
> > It looks like could not cover the case: req->tp_block_nr = 2 ->
> reg->tp_block_nr = 1 .
> >
> 
> Oh, looks like this case would never happen, so I think your solution is ok.
> 
> > what about this way:
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -4331,13 +4331,17 @@ static int packet_set_ring(struct sock *sk, union
> tpacket_req_u *req_u,
> >                 register_prot_hook(sk);
> >         }
> >         spin_unlock(&po->bind_lock);
> > -       if (closing && (po->tp_version > TPACKET_V2)) {
> > +       if ((closing || (pg_vec && !reg->tp_block_nr))&&
> > + (po->tp_version > TPACKET_V2)) {
> >                 /* Because we don't support block-based V3 on tx-ring */
> >                 if (!tx_ring)
> >                         prb_shutdown_retire_blk_timer(po,
> rb_queue);
> >
> >
> 
> >>
> >
> >
> > .
> >