Jesper Dangaard Brouer <brouer@xxxxxxxxxx> wrote: [ CC'd Patrick ] > I'm hitting this general protection fault, when unloading iptables_nat. > [ 524.591067] Pid: 5842, comm: modprobe Not tainted 3.6.0-rc3-pablo-nf-next+ #1 Red Hat KVM > [ 524.591067] RIP: 0010:[<ffffffffa002c2fd>] [<ffffffffa002c2fd>] nf_nat_proto_clean+0x6d/0xc0 [nf_nat] > [ 524.591067] RSP: 0018:ffff880073203e18 EFLAGS: 00010246 > [ 524.591067] RAX: 0000000000000000 RBX: ffff880077dff2c8 RCX: ffff8800797fab70 > [ 524.591067] RDX: dead000000200200 RSI: ffff880073203e88 RDI: ffffffffa002f208 > [ 524.591067] RBP: ffff880073203e28 R08: ffff880073202000 R09: 0000000000000000 > [ 524.591067] R10: dead000000200200 R11: dead000000100100 R12: ffffffff81c6dc00 > list corruption? ^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^ Yep, looks like it. > [ 524.591067] [<ffffffffa002c290>] ? nf_nat_net_exit+0x50/0x50 [nf_nat] > [ 524.591067] [<ffffffff815614e3>] nf_ct_iterate_cleanup+0xc3/0x170 > [ 524.591067] [<ffffffffa002c54a>] nf_nat_l3proto_unregister+0x8a/0x100 [nf_nat] > [ 524.591067] [<ffffffff812a0303>] ? compat_prepare_timeout+0x13/0xb0 > [ 524.591067] [<ffffffffa0035848>] nf_nat_l3proto_ipv4_exit+0x10/0x23 [nf_nat_ipv4] On module removal nf_nat_ipv4 calls nf_iterate_cleanup which invokes nf_nat_proto_clean() for each conntrack. That will then call hlist_del_rcu(&nat->bysource) using eachs conntracks nat ext area. Problem is that nf_nat_proto_clean() is called multiple times for the same conntrack: a) nf_ct_iterate_cleanup() returns each ct twice (origin, reply) b) we call it both for l3 and for l4 protocol ids We barf in hlist_del_rcu the 2nd time because ->pprev is poisoned. This was introduced with the ipv6 nat patches. --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -487,7 +487,7 @@ static int nf_nat_proto_clean(struct nf_conn *i, void *data) if (clean->hash) { spin_lock_bh(&nf_nat_lock); - hlist_del_rcu(&nat->bysource); + hlist_del_init_rcu(&nat->bysource); spin_unlock_bh(&nf_nat_lock); } else { Would probably avoid it. I guess it would be nicer to only call this once for each ct. Patrick, any other idea? -- 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