RE: af_packet: use after free in prb_retire_rx_blk_timer_expired

[liujian (CE)]

Hi, 

Do we need delete the v3 ring, when tp_version changed from TPACKET_V3 to TPACKET_V1 ?


Best Regards,
liujian


> -----Original Message-----
> From: liujian (CE)
> Sent: Sunday, July 23, 2017 4:21 PM
> To: 'Cong Wang'; Dingtianhong
> 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
> 
> Hi Wang Cong,
> 
> With this patch , the system was crashed when setsockopt.
> 
> The call trace as below:
> 
> crash> bt
> PID: 3069   TASK: ffff8800afcc0000  CPU: 0   COMMAND: "trinity-main"
>  #0 [ffff8801bec03ce0] machine_kexec at ffffffff8105354b
>  #1 [ffff8801bec03d40] crash_kexec at ffffffff810f7e82
>  #2 [ffff8801bec03e10] panic at ffffffff81650058
>  #3 [ffff8801bec03e90] watchdog_timer_fn at ffffffff81122533
>  #4 [ffff8801bec03ec8] __hrtimer_run_queues at ffffffff810abeb2
>  #5 [ffff8801bec03f20] hrtimer_interrupt at ffffffff810ac450
>  #6 [ffff8801bec03f70] local_apic_timer_interrupt at ffffffff8104a457
>  #7 [ffff8801bec03f88] smp_apic_timer_interrupt at ffffffff8166aed0
>  #8 [ffff8801bec03fb0] apic_timer_interrupt at ffffffff8166931d
> --- <IRQ stack> ---
>  #9 [ffff8801b301fcb8] apic_timer_interrupt at ffffffff8166931d
>     [exception RIP: lock_timer_base+77]
>     RIP: ffffffff8108dced  RSP: ffff8801b301fd60  RFLAGS: 00000246
>     RAX: 0000000000000000  RBX: ffff8800afcc0000  RCX:
> 0000000000000001
>     RDX: ffff8800afcc0000  RSI: ffff8801b301fd90  RDI: ffff8800b0d853c8
>     RBP: ffff8801b301fd80   R8: ffff8800afcc0000   R9: ffffea0002680000
>     R10: 000000000000003c  R11: ffff8801b301fb2e  R12: ffff8800afcc0000
>     R13: ffff8800afcc0000  R14: 0000000000000000  R15: ffffffff83d1a340
>     ORIG_RAX: ffffffffffffff10  CS: 0010  SS: 0018
> #10 [ffff8801b301fd88] try_to_del_timer_sync at ffffffff8108f19f
> #11 [ffff8801b301fdb8] del_timer_sync at ffffffff8108f252
> #12 [ffff8801b301fdd0] packet_set_ring at ffffffff81635e60
> #13 [ffff8801b301fe98] packet_setsockopt at ffffffff81636760
> #14 [ffff8801b301ff38] sys_setsockopt at ffffffff81531860
> #15 [ffff8801b301ff80] tracesys at ffffffff816687ed (via system_call)
>     RIP: 00007fcc78b03e3a  RSP: 00007fff16f246b8  RFLAGS: 00000202
>     RAX: ffffffffffffffda  RBX: ffffffff816687ed  RCX: ffffffffffffffff
>     RDX: 0000000000000005  RSI: 0000000000000107  RDI:
> 0000000000000180
>     RBP: 0000000000000180   R8: 000000000000001c   R9:
> 00007fcc78dc7160
>     R10: 0000000001fd6ba0  R11: 0000000000000202  R12:
> 0000000000000000
>     R13: 0000000000000011  R14: 0000000001fd6b60  R15:
> 0000000001fd6b70
>     ORIG_RAX: 0000000000000036  CS: 0033  SS: 002b
> 
> 
> Best Regards,
> liujian
> 
> 
> > -----Original Message-----
> > From: Cong Wang [mailto:xiyou.wangcong@xxxxxxxxx]
> > Sent: Sunday, July 23, 2017 1:59 PM
> > To: Dingtianhong
> > Cc: liujian (CE); 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 Sat, Jul 22, 2017 at 8:40 PM, Ding Tianhong
> > <dingtianhong@xxxxxxxxxx>
> > wrote:
> > > Hi, Cong:
> > >
> > > Thanks for your quirk solution, but I still has some doubts about
> > > it, it looks like fix the problem in the
> > > packet_setsockopt->packet_set_ring processing, but when in
> > > packet_release processing, it may could not release the real pg_vec
> > > for the TPACKET_V3 ring, and then cause the mem leak, maybe I miss
> > > something here, nice to hear from your feedback. :)
> >
> > Yes you miss that packet_release() has memset()'s so we won't hit that
> > path. :)
> >
> > However, I missed the swap() in this messy function, actually I
> > believe the bug is that we modify tpacket_kbdq_core inside rx_ring in
> > non-closing case without actually stopping its timer. I feel more confident
> with the following patch:
> >
> >
> > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index
> > 008bb34ee324..267b181fef15 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -4263,6 +4263,7 @@ static int packet_set_ring(struct sock *sk,
> > union tpacket_req_u *req_u,
> >                 case TPACKET_V3:
> >                         /* Block transmit is not supported yet */
> >                         if (!tx_ring) {
> > +                               prb_shutdown_retire_blk_timer(po,
> > + rb_queue);
> >                                 init_prb_bdqc(po, rb, pg_vec, req_u);
> >                         } else {
> >                                 struct tpacket_req3 *req3 =
> > &req_u->req3;