On Wed, Apr 10, 2013 at 11:32:04AM +0200, Florian Westphal wrote:
> Patrick McHardy <kaber@xxxxxxxxx> wrote:
> > On Wed, Apr 10, 2013 at 11:04:36AM +0200, Florian Westphal wrote:
> > > Subject: Re: [BUG] Fatal exception in interrupt - nf_nat_cleanup_conntrack during IPv6 tests
> > > CAI Qian <caiqian@xxxxxxxxxx> wrote:
> > > > Just hit this very often during IPv6 tests in both the latest stable
> > > > and mainline kernel.
> > > >
> > > > [ 3597.206166] Modules linked in:
> > > [..]
> > > > nf_nat_ipv4(F-)
> > > [..]
> > >
> > > > [ 3597.804861] RIP: 0010:[<ffffffffa03227f2>] [<ffffffffa03227f2>] nf_nat_cleanup_conntrack+0x42/0x70 [nf_nat]
> > > > [ 3597.855207] RSP: 0018:ffff880202c63d40 EFLAGS: 00010246
> > > > [ 3597.881350] RAX: 0000000000000000 RBX: ffff8801ac7bec28 RCX: ffff8801d0eedbe0
> > > > [ 3597.917226] RDX: dead000000200200 RSI: 0000000000000011 RDI: ffffffffa03265b8
> > > [..]
> > >
> > > > [ 3598.421036] <IRQ>
> > > > [ 3598.430467] [<ffffffffa0305bb4>] __nf_ct_ext_destroy+0x44/0x60 [nf_conntrack]
> > > > [ 3598.499191] [<ffffffffa02fd3fe>] nf_conntrack_free+0x2e/0x70 [nf_conntrack]
> > > > [ 3598.534121] [<ffffffffa02febed>] destroy_conntrack+0xbd/0x110 [nf_conntrack]
> > > > [ 3598.569981] [<ffffffff81532187>] nf_conntrack_destroy+0x17/0x20
> > > > [ 3598.599579] [<ffffffffa02fe77c>] death_by_timeout+0xdc/0x1b0 [nf_conntrack]
> > > [..]
> > > > [ 3599.241868] Code: 83 ec 08 0f b6 58 11 84 db 74 43 48 01 c3 48 83 7b 20 00 74 39 48 c7 c7 b8 65 32 a0 e8 98 fc 2e e1 48 8b 03 48 8b 53 08 48 85 c0 <48> 89 02 74 04 48 89 50 08 48 ba 00 02 20 00 00 00 ad de 48 c7
> > > > [ 3599.337037] RIP [<ffffffffa03227f2>] nf_nat_cleanup_conntrack+0x42/0x70 [nf_nat]
> > >
> > > Looks like we tried to remove bysource hash twice (rdx is
> > > LIST_POISON_2).
> > >
> > > I wonder if this would explain it:
> > >
> > > static void nf_nat_l4proto_clean(u8 l3proto, u8 l4proto)
> > > {
> > > [..]
> > > /* Step 1 - remove from bysource hash */
> > > clean.hash = true;
> > > for_each_net(net)
> > > nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);
> > >
> > > A nfct->timer fires and a conntrack is free'd before step 2 memsets the
> > > nat extension. In that case, we would try to delete nat->bysource
> > > again?
> >
> > Not sure I follow, we only invoke nf_nat_l4proto_clean() through
> > nf_nat_l4proto_unregister(), right?
> >
> > Did this happen during module unload?
>
> Looks like it, nf_nat_ipv4 is listed as F- in the oops trace. (afaics,
> "-" means "module going away").
Yes, that seems like a real race condition. We probably could extend the
nf_nat_lock sections to avoid this, but I wonder wether we should just kill
those conntracks, the connections are not going to work after being
"de-nated" anymore anyway.
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
