Date:   Thu, 12 Apr 2018 10:03:48 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+b202b7208664142954fa@...kaller.appspotmail.com>
Cc:     bpoirier@...e.com, David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mike Maloney <maloney@...gle.com>,
        netdev <netdev@...r.kernel.org>, rami.rosen@...el.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Willem de Bruijn <willemb@...gle.com>,
        makita.toshiaki@....ntt.co.jp
Subject: Re: KMSAN: uninit-value in __netif_receive_skb_core

On Thu, Apr 12, 2018 at 10:01 AM, syzbot
<syzbot+b202b7208664142954fa@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on https://github.com/google/kmsan.git/master
> commit
> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +0000)
> kmsan: temporarily disable visitAsmInstruction() to help syzbot
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=b202b7208664142954fa
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5356516437655552
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
> compiler: clang version 7.0.0 (trunk 329391)

+Toshiaki as this seems to be related to the recent vlan tagging changes.
This also seems to be related to
https://groups.google.com/d/msg/syzkaller-bugs/VRH9NnUi2k0/90GYsAeRBgAJ

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b202b7208664142954fa@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> ==================================================================
> BUG: KMSAN: uninit-value in __read_once_size include/linux/compiler.h:197
> [inline]
> BUG: KMSAN: uninit-value in deliver_ptype_list_skb net/core/dev.c:1908
> [inline]
> BUG: KMSAN: uninit-value in __netif_receive_skb_core+0x4630/0x4a80
> net/core/dev.c:4545
> CPU: 0 PID: 5999 Comm: syz-executor3 Not tainted 4.16.0+ #82
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>  __read_once_size include/linux/compiler.h:197 [inline]
>  deliver_ptype_list_skb net/core/dev.c:1908 [inline]
>  __netif_receive_skb_core+0x4630/0x4a80 net/core/dev.c:4545
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1040
>  </IRQ>
>  do_softirq kernel/softirq.c:329 [inline]
>  __local_bh_enable_ip+0x114/0x140 kernel/softirq.c:182
>  local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
>  rcu_read_unlock_bh include/linux/rcupdate.h:726 [inline]
>  __dev_queue_xmit+0x2a31/0x2b60 net/core/dev.c:3584
>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>  packet_snd net/packet/af_packet.c:2944 [inline]
>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg net/socket.c:640 [inline]
>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>  vfs_writev fs/read_write.c:977 [inline]
>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> RIP: 0033:0x455259
> RSP: 002b:00007fb53ede8c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
> RAX: ffffffffffffffda RBX: 00007fb53ede96d4 RCX: 0000000000455259
> RDX: 0000000000000001 RSI: 00000000200010c0 RDI: 0000000000000013
> RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000000006cd R14: 00000000006fd3d8 R15: 0000000000000000
>
> Uninit was stored to memory at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
>  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
>  __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:521
>  skb_vlan_untag+0x950/0xee0 include/linux/if_vlan.h:597
>  __netif_receive_skb_core+0x70a/0x4a80 net/core/dev.c:4460
>  __netif_receive_skb net/core/dev.c:4627 [inline]
>  process_backlog+0x62d/0xe20 net/core/dev.c:5307
>  napi_poll net/core/dev.c:5705 [inline]
>  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5771
>  __do_softirq+0x56d/0x93d kernel/softirq.c:285
> Uninit was created at:
>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
>  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
>  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
>  slab_post_alloc_hook mm/slab.h:445 [inline]
>  slab_alloc_node mm/slub.c:2737 [inline]
>  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
>  __kmalloc_reserve net/core/skbuff.c:138 [inline]
>  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
>  alloc_skb include/linux/skbuff.h:984 [inline]
>  alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
>  sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085
>  packet_alloc_skb net/packet/af_packet.c:2803 [inline]
>  packet_snd net/packet/af_packet.c:2894 [inline]
>  packet_sendmsg+0x6444/0x8a10 net/packet/af_packet.c:2969
>  sock_sendmsg_nosec net/socket.c:630 [inline]
>  sock_sendmsg net/socket.c:640 [inline]
>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>  vfs_writev fs/read_write.c:977 [inline]
>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
> ==================================================================
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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