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Date:   Fri, 10 Aug 2018 09:20:59 -0700
From:   William Tu <u9012063@...il.com>
To:     syzbot <syzbot+4a2c52677a8a1aa283cb@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: KMSAN: uninit-value in ip_tunnel_xmit (2)

On Fri, Aug 10, 2018 at 7:30 AM, syzbot
<syzbot+4a2c52677a8a1aa283cb@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    80ecacc456c1 kmsan: fix CONFIG_KMSAN=n build
> git tree:       https://github.com/google/kmsan.git/master
> console output: https://syzkaller.appspot.com/x/log.txt?x=163b7794400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=93d57043084eee38
> dashboard link: https://syzkaller.appspot.com/bug?extid=4a2c52677a8a1aa283cb
> compiler:       clang version 7.0.0 (trunk 334104)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=17cec9dc400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=145dcf0c400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+4a2c52677a8a1aa283cb@...kaller.appspotmail.com
>
> IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
> IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
> IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
> 8021q: adding VLAN 0 to HW filter on device team0
> ==================================================================
> BUG: KMSAN: uninit-value in ip_tunnel_xmit+0x63a/0x3b10 net/ipv4/ip_tunnel.c:645


It complains about
 644         dst = tnl_params->daddr;
 645         if (dst == 0) {

I guess at __gre_tunnel_init, we have to zero the tunne->parms.iph.

I will test it to see if the issue go away.

Thanks
William

> CPU: 1 PID: 4603 Comm: syz-executor712 Not tainted 4.18.0-rc4+ #27
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x185/0x1e0 lib/dump_stack.c:113
>  kmsan_report+0x195/0x2c0 mm/kmsan/kmsan.c:982
>  __msan_warning+0x7d/0xe0 mm/kmsan/kmsan_instr.c:645
>  ip_tunnel_xmit+0x63a/0x3b10 net/ipv4/ip_tunnel.c:645
>  __gre_xmit net/ipv4/ip_gre.c:449 [inline]
>  ipgre_xmit+0xe16/0xef0 net/ipv4/ip_gre.c:701
>  __netdev_start_xmit include/linux/netdevice.h:4148 [inline]
>  netdev_start_xmit include/linux/netdevice.h:4157 [inline]
>  xmit_one net/core/dev.c:3034 [inline]
>  dev_hard_start_xmit+0x60f/0xcc0 net/core/dev.c:3050
>  __dev_queue_xmit+0x3060/0x3c70 net/core/dev.c:3569
>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3602
>  packet_snd net/packet/af_packet.c:2919 [inline]
>  packet_sendmsg+0x8469/0x9010 net/packet/af_packet.c:2944
>  sock_sendmsg_nosec net/socket.c:641 [inline]
>  sock_sendmsg net/socket.c:651 [inline]
>  ___sys_sendmsg+0xed9/0x1350 net/socket.c:2125
>  __sys_sendmsg net/socket.c:2163 [inline]
>  __do_sys_sendmsg net/socket.c:2172 [inline]
>  __se_sys_sendmsg net/socket.c:2170 [inline]
>  __x64_sys_sendmsg+0x3b0/0x520 net/socket.c:2170
>  do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x63/0xe7
> RIP: 0033:0x4412f9
> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffdc77f10d8 EFLAGS: 00000213 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004412f9
> RDX: 0000000000000000 RSI: 0000000020000600 RDI: 0000000000000003
> RBP: 00000000006cc018 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000020 R11: 0000000000000213 R12: 0000000000402260
> R13: 00000000004022f0 R14: 0000000000000000 R15: 0000000000000000
>
> Uninit was created at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline]
>  kmsan_internal_poison_shadow+0xc8/0x1d0 mm/kmsan/kmsan.c:181
>  kmsan_kmalloc+0xa1/0x120 mm/kmsan/kmsan_hooks.c:91
>  kmsan_slab_alloc+0x10/0x20 mm/kmsan/kmsan_hooks.c:100
>  slab_post_alloc_hook mm/slab.h:446 [inline]
>  slab_alloc_node mm/slub.c:2720 [inline]
>  __kmalloc_node_track_caller+0xb48/0x11d0 mm/slub.c:4353
>  __kmalloc_reserve net/core/skbuff.c:138 [inline]
>  __alloc_skb+0x2cb/0x9e0 net/core/skbuff.c:206
>  alloc_skb include/linux/skbuff.h:988 [inline]
>  alloc_skb_with_frags+0x1e6/0xb80 net/core/skbuff.c:5271
>  sock_alloc_send_pskb+0xb59/0x11e0 net/core/sock.c:2095
>  packet_alloc_skb net/packet/af_packet.c:2776 [inline]
>  packet_snd net/packet/af_packet.c:2867 [inline]
>  packet_sendmsg+0x68cb/0x9010 net/packet/af_packet.c:2944
>  sock_sendmsg_nosec net/socket.c:641 [inline]
>  sock_sendmsg net/socket.c:651 [inline]
>  ___sys_sendmsg+0xed9/0x1350 net/socket.c:2125
>  __sys_sendmsg net/socket.c:2163 [inline]
>  __do_sys_sendmsg net/socket.c:2172 [inline]
>  __se_sys_sendmsg net/socket.c:2170 [inline]
>  __x64_sys_sendmsg+0x3b0/0x520 net/socket.c:2170
>  do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x63/0xe7
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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