Re: [syzbot] kernel BUG in __skb_gso_segment

[Eric Dumazet]

On Fri, Jun 3, 2022 at 6:02 PM syzbot
<syzbot+7160965e6a93d826048a@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    2c5ca23f7414 Merge tag 'ovl-update-5.19' of git://git.kern..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=11330935f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9b19cdd2d45cc221
> dashboard link: https://syzkaller.appspot.com/bug?extid=7160965e6a93d826048a
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1724add5f00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1324cbf9f00000
>
> The issue was bisected to:
>
> commit dfed913e8b55a0c2c4906f1242fd38fd9a116e49
> Author: Hangbin Liu <liuhangbin@xxxxxxxxx>
> Date:   Mon Apr 25 01:45:02 2022 +0000
>
>     net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=169079bdf00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=159079bdf00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=119079bdf00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7160965e6a93d826048a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: dfed913e8b55 ("net/af_packet: add VLAN support for AF_PACKET SOCK_RAW GSO")
>
> ------------[ cut here ]------------
> kernel BUG at include/linux/skbuff.h:2699!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 3601 Comm: syz-executor210 Not tainted 5.18.0-syzkaller-11338-g2c5ca23f7414 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__skb_pull include/linux/skbuff.h:2699 [inline]
> RIP: 0010:skb_mac_gso_segment+0x48f/0x530 net/core/gro.c:136
> Code: 00 48 c7 c7 00 96 d4 8a c6 05 cb d3 45 06 01 e8 26 bb d0 01 e9 2f fd ff ff 49 c7 c4 ea ff ff ff e9 f1 fe ff ff e8 91 84 19 fa <0f> 0b 48 89 df e8 97 44 66 fa e9 7f fd ff ff e8 ad 44 66 fa e9 48
> RSP: 0018:ffffc90002e2f4b8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000
> RDX: ffff88805bb58000 RSI: ffffffff8760ed0f RDI: 0000000000000004
> RBP: 0000000000005dbc R08: 0000000000000004 R09: 0000000000000fe0
> R10: 0000000000000fe4 R11: 0000000000000000 R12: 0000000000000fe0
> R13: ffff88807194d780 R14: 1ffff920005c5e9b R15: 0000000000000012
> FS:  000055555730f300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200015c0 CR3: 0000000071ff8000 CR4: 0000000000350ee0
> Call Trace:
>  <TASK>
>  __skb_gso_segment+0x327/0x6e0 net/core/dev.c:3411
>  skb_gso_segment include/linux/netdevice.h:4749 [inline]
>  validate_xmit_skb+0x6bc/0xf10 net/core/dev.c:3669
>  validate_xmit_skb_list+0xbc/0x120 net/core/dev.c:3719
>  sch_direct_xmit+0x3d1/0xbe0 net/sched/sch_generic.c:327
>  __dev_xmit_skb net/core/dev.c:3815 [inline]
>  __dev_queue_xmit+0x14a1/0x3a00 net/core/dev.c:4219
>  packet_snd net/packet/af_packet.c:3071 [inline]
>  packet_sendmsg+0x21cb/0x5550 net/packet/af_packet.c:3102
>  sock_sendmsg_nosec net/socket.c:714 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:734
>  ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2546
>  __sys_sendmsg net/socket.c:2575 [inline]
>  __do_sys_sendmsg net/socket.c:2584 [inline]
>  __se_sys_sendmsg net/socket.c:2582 [inline]
>  __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0
> RIP: 0033:0x7f4b95da06c9
> Code: 28 c3 e8 4a 15 00 00 66 2e 0f 1f 84 00 00 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffd7defc4c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00007ffd7defc4f0 RCX: 00007f4b95da06c9
> RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> RBP: 0000000000000003 R08: bb1414ac00000050 R09: bb1414ac00000050
> R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffd7defc4e0 R14: 00007ffd7defc4d8 R15: 00007ffd7defc4d4
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__skb_pull include/linux/skbuff.h:2699 [inline]
> RIP: 0010:skb_mac_gso_segment+0x48f/0x530 net/core/gro.c:136
> Code: 00 48 c7 c7 00 96 d4 8a c6 05 cb d3 45 06 01 e8 26 bb d0 01 e9 2f fd ff ff 49 c7 c4 ea ff ff ff e9 f1 fe ff ff e8 91 84 19 fa <0f> 0b 48 89 df e8 97 44 66 fa e9 7f fd ff ff e8 ad 44 66 fa e9 48
> RSP: 0018:ffffc90002e2f4b8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000012 RCX: 0000000000000000
> RDX: ffff88805bb58000 RSI: ffffffff8760ed0f RDI: 0000000000000004
> RBP: 0000000000005dbc R08: 0000000000000004 R09: 0000000000000fe0
> R10: 0000000000000fe4 R11: 0000000000000000 R12: 0000000000000fe0
> R13: ffff88807194d780 R14: 1ffff920005c5e9b R15: 0000000000000012
> FS:  000055555730f300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200015c0 CR3: 0000000071ff8000 CR4: 0000000000350ee0
>
>
> ---
> This report 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@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

#syz fix: net/af_packet: make sure to pull mac header