On Wed, 2013-03-06 at 10:59 -0500, Dave Jones wrote:
> I know 3.7.9 is EOL, but this code doesn't look like it's changed in current.
> (unless the cause/fix was in code unrelated to these paths)
> 
> A user reported the following GPF..
> 
> general protection fault: 0000 [#1] SMP 
> Modules linked in: ipheth fuse ebtable_nat xt_CHECKSUM bridge stp llc ip6t_REJECT iptable_mangle nf_conntrack(-) ebtable_filter ebtables snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_page_alloc hp_wmi snd_timer coretemp iTCO_wdt tg3 snd sparse_keymap rfkill soundcore iTCO_vendor_support lpc_ich i7core_edac edac_core serio_raw microcode mfd_core vhost_net tun macvtap macvlan kvm_intel kvm binfmt_misc uinput nouveau mxm_wmi crc32c_intel video i2c_algo_bit drm_kms_helper ttm firewire_ohci firewire_core drm crc_itu_t i2c_core wmi [last unloaded: xt_conntrack]
> CPU 2 
> Pid: 25407, comm: qemu-kvm Not tainted 3.7.9-205.fc18.x86_64 #1 Hewlett-Packard HP Z400 Workstation/0B4Ch
> RIP: 0010:[<ffffffffa0399bd5>]  [<ffffffffa0399bd5>] destroy_conntrack+0x35/0x120 [nf_conntrack]
> RSP: 0018:ffff880276913d78  EFLAGS: 00010206
> RAX: 50626b6b7876376c RBX: ffff88026e530d68 RCX: ffff88028d158e00
> RDX: ffff88026d0d5470 RSI: 0000000000000011 RDI: 0000000000000002
> RBP: ffff880276913d88 R08: 0000000000000000 R09: ffff880295002900
> R10: 0000000000000000 R11: 0000000000000003 R12: ffffffff81ca3b40
> R13: ffffffff8151a8e0 R14: ffff880270875000 R15: 0000000000000002
> FS:  00007ff3bce38a00(0000) GS:ffff88029fc40000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 00007fd1430bd000 CR3: 000000027042b000 CR4: 00000000000027e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process qemu-kvm (pid: 25407, threadinfo ffff880276912000, task ffff88028c369720)
> Stack:
>  ffff880156f59100 ffff880156f59100 ffff880276913d98 ffffffff815534f7
>  ffff880276913db8 ffffffff8151a74b ffff880270875000 ffff880156f59100
>  ffff880276913dd8 ffffffff8151a5a6 ffff880276913dd8 ffff88026d0d5470
> Call Trace:
>  [<ffffffff815534f7>] nf_conntrack_destroy+0x17/0x20
>  [<ffffffff8151a74b>] skb_release_head_state+0x7b/0x100
>  [<ffffffff8151a5a6>] __kfree_skb+0x16/0xa0
>  [<ffffffff8151a666>] kfree_skb+0x36/0xa0
>  [<ffffffff8151a8e0>] skb_queue_purge+0x20/0x40
>  [<ffffffffa02205f7>] __tun_detach+0x117/0x140 [tun]
>  [<ffffffffa022184c>] tun_chr_close+0x3c/0xd0 [tun]
>  [<ffffffff8119669c>] __fput+0xec/0x240
>  [<ffffffff811967fe>] ____fput+0xe/0x10
>  [<ffffffff8107eb27>] task_work_run+0xa7/0xe0
>  [<ffffffff810149e1>] do_notify_resume+0x71/0xb0
>  [<ffffffff81640152>] int_signal+0x12/0x17
> Code: 00 00 04 48 89 e5 41 54 53 48 89 fb 4c 8b a7 e8 00 00 00 0f 85 de 00 00 00 0f b6 73 3e 0f b7 7b 2a e8 10 40 00 00 48 85 c0 74 0e <48> 8b 40 28 48 85 c0 74 05 48 89 df ff d0 48 c7 c7 08 6a 3a a0 
> RIP  [<ffffffffa0399bd5>] destroy_conntrack+0x35/0x120 [nf_conntrack]
>  RSP <ffff880276913d78>
> 
> 
> 
>         /* To make sure we don't get any weird locking issues here:
>          * destroy_conntrack() MUST NOT be called with a write lock
>          * to nf_conntrack_lock!!! -HW */
>         rcu_read_lock();
>         l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
>     1378:       0f b6 b3 86 00 00 00    movzbl 0x86(%rbx),%esi
>     137f:       0f b7 7b 72             movzwl 0x72(%rbx),%edi
>     1383:       e8 00 00 00 00          callq  1388 <destroy_conntrack+0x78>
>         if (l4proto && l4proto->destroy)
>     1388:       48 85 c0                test   %rax,%rax
>     138b:       74 0e                   je     139b <destroy_conntrack+0x8b>
>     138d:       48 8b 40 28             mov    0x28(%rax),%rax    <-----  HERE
>     1391:       48 85 c0                test   %rax,%rax
>     1394:       74 05                   je     139b <destroy_conntrack+0x8b>
>                 l4proto->destroy(ct);
>     1396:       48 89 df                mov    %rbx,%rdi
>     1399:       ff d0                   callq  *%rax
> 
> 
> l4proto (%rax) is garbage (0x50626b6b7876376c) which looks a little like ascii,
> but P>kkxv7l doesn't mean much to me.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=917792 is the original report, but
> there aren't any further details yet.
> 
> 	Dave
> 

tun driver lacks a nf_reset(skb) call

I would try :

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2c6a22e..b7c457a 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -747,6 +747,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto drop;
 	skb_orphan(skb);
 
+	nf_reset(skb);
+
 	/* Enqueue packet */
 	skb_queue_tail(&tfile->socket.sk->sk_receive_queue, skb);