Date:   Wed, 25 Nov 2020 21:54:29 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Dmitry Vyukov <dvyukov@...gle.com>
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

Hi Dmitry,

On 25.11.20 19:48, Dmitry Vyukov wrote:
> On Wed, Nov 25, 2020 at 5:04 PM Oliver Hartkopp <socketcan@...tkopp.net> wrote:

>> 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?
> 

> 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.
I already prepared a patch for it which has indeed 90% explanatory 
comment ;-)

Will send out a patch tomorrow after collecting all the three/four? 
syskaller bug IDs that popped up with this issue :-D

Many thanks!
Oliver


> 
> 
> 
> 
>> 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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