Message-ID: <CACT4Y+aAtWO5r+VCxqN0UFn-S1OEvDe5QS3r44kXSeA7mfhUMw@mail.gmail.com>
Date:   Wed, 25 Nov 2020 19:48:00 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Oliver Hartkopp <socketcan@...tkopp.net>
Cc:     syzbot <syzbot+381d06e0c8eaacb8706f@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-can@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: BUG: receive list entry not found for dev vxcan1, id 002, mask C00007FF

On Wed, Nov 25, 2020 at 5:04 PM Oliver Hartkopp <socketcan@...tkopp.net> wrote:
>
> Hello all,
>
> AFAICS the problems are caused by the WARN() statement here:
>
> https://elixir.bootlin.com/linux/v5.10-rc4/source/net/can/af_can.c#L546
>
> The idea was to check whether CAN protocol implementations work
> correctly on their filter lists.
>
> With the fault injection it seem like we're getting a race between
> closing the socket and removing the netdevice.
>
> This seems to be very seldom but it does not break anything.
>
> Would removing the WARN(1) or replacing it with pr_warn() be ok to close
> this issue?

Hi Oliver,

Yes, this is the intended way to deal with this:
https://elixir.bootlin.com/linux/v5.10-rc5/source/include/asm-generic/bug.h#L75

Maybe a good opportunity to add some explanatory comment as well
regarding how it should not happen but can.

Thanks for looking into this.




> On 23.11.20 12:58, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    c2e7554e Merge tag 'gfs2-v5.10-rc4-fixes' of git://git.ker..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=117f03ba500000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=75292221eb79ace2
> > dashboard link: https://syzkaller.appspot.com/bug?extid=381d06e0c8eaacb8706f
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+381d06e0c8eaacb8706f@...kaller.appspotmail.com
> >
> > ------------[ cut here ]------------
> > BUG: receive list entry not found for dev vxcan1, id 002, mask C00007FF
> > WARNING: CPU: 1 PID: 12946 at net/can/af_can.c:546 can_rx_unregister+0x5a4/0x700 net/can/af_can.c:546
> > Modules linked in:
> > CPU: 1 PID: 12946 Comm: syz-executor.1 Not tainted 5.10.0-rc4-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > RIP: 0010:can_rx_unregister+0x5a4/0x700 net/can/af_can.c:546
> > Code: 8b 7c 24 78 44 8b 64 24 68 49 c7 c5 20 ac 56 8a e8 01 6c 97 f9 44 89 f9 44 89 e2 4c 89 ee 48 c7 c7 60 ac 56 8a e8 66 af d3 00 <0f> 0b 48 8b 7c 24 28 e8 b0 25 0f 01 e9 54 fb ff ff e8 26 e0 d8 f9
> > RSP: 0018:ffffc90017e2fb38 EFLAGS: 00010286
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> > RDX: ffff8880147a8000 RSI: ffffffff8158f3c5 RDI: fffff52002fc5f59
> > RBP: 0000000000000118 R08: 0000000000000001 R09: ffff8880b9f2011b
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
> > R13: ffff8880254c0000 R14: 1ffff92002fc5f6e R15: 00000000c00007ff
> > FS:  0000000001ddc940(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000001b2f121000 CR3: 00000000152c0000 CR4: 00000000001506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   isotp_notifier+0x2a7/0x540 net/can/isotp.c:1303
> >   call_netdevice_notifier net/core/dev.c:1735 [inline]
> >   call_netdevice_unregister_notifiers+0x156/0x1c0 net/core/dev.c:1763
> >   call_netdevice_unregister_net_notifiers net/core/dev.c:1791 [inline]
> >   unregister_netdevice_notifier+0xcd/0x170 net/core/dev.c:1870
> >   isotp_release+0x136/0x600 net/can/isotp.c:1011
> >   __sock_release+0xcd/0x280 net/socket.c:596
> >   sock_close+0x18/0x20 net/socket.c:1277
> >   __fput+0x285/0x920 fs/file_table.c:281
> >   task_work_run+0xdd/0x190 kernel/task_work.c:151
> >   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
> >   exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
> >   exit_to_user_mode_prepare+0x17e/0x1a0 kernel/entry/common.c:191
> >   syscall_exit_to_user_mode+0x38/0x260 kernel/entry/common.c:266
> >   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x417811
> > Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 1a 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
> > RSP: 002b:000000000169fbf0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
> > RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000417811
> > RDX: 0000000000000000 RSI: 00000000000013b7 RDI: 0000000000000003
> > RBP: 0000000000000001 R08: 00000000acabb3b7 R09: 00000000acabb3bb
> > R10: 000000000169fcd0 R11: 0000000000000293 R12: 000000000118c9a0
> > R13: 000000000118c9a0 R14: 00000000000003e8 R15: 000000000118bf2c
> >
> >
> > ---
> > 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@...glegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
>
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