general protection fault in dropmon_net_event

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1189a543b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=1748c3a6354247cbbd9d
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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+1748c3...@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 853 Comm: kworker/u4:3 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
RIP: 0010:dropmon_net_event+0xd1/0x470 net/core/drop_monitor.c:341
Code: 00 00 e8 b2 02 df fa 49 bc 00 00 00 00 00 fc ff df 44 8b 35 d1 0c 54 07 eb 36 e8 9a 02 df fa 4c 8d 7b 10 4c 89 f8 48 c1 e8 03 <42> 80 3c 20 00 0f 85 d7 02 00 00 48 8b 43 10 48 89 dd 48 83 e8 10
RSP: 0018:ffff8880b3dc7920 EFLAGS: 00010a02
RAX: 1fe01ad80d18cd02 RBX: ff00d6c068c66800 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff868382d6 RDI: 0000000000000001
RBP: ffff88800015f400 R08: 0000000000000000 R09: fffffbfff15c8ff4
R10: ffffffff8ae47fa7 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880952e0340 R14: 0000000000000001 R15: ff00d6c068c66810
FS: 0000000000000000(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c02cead000 CR3: 000000003f3f2000 CR4: 00000000003426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
notifier_call_chain+0xc0/0x230 kernel/notifier.c:93
call_netdevice_notifiers net/core/dev.c:1762 [inline]
rollback_registered_many+0x83e/0xe70 net/core/dev.c:8196
unregister_netdevice_many.part.0+0x1a/0x300 net/core/dev.c:9324
unregister_netdevice_many+0x36/0x50 net/core/dev.c:9323
sit_exit_batch_net+0x543/0x700 net/ipv6/sit.c:1893
ops_exit_list+0xf9/0x150 net/core/net_namespace.c:156
cleanup_net+0x3b4/0x8b0 net/core/net_namespace.c:554
process_one_work+0x864/0x1570 kernel/workqueue.c:2153
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Modules linked in:
---[ end trace 8a1ef184a2ffeed4 ]---
RIP: 0010:dropmon_net_event+0xd1/0x470 net/core/drop_monitor.c:341
Code: 00 00 e8 b2 02 df fa 49 bc 00 00 00 00 00 fc ff df 44 8b 35 d1 0c 54 07 eb 36 e8 9a 02 df fa 4c 8d 7b 10 4c 89 f8 48 c1 e8 03 <42> 80 3c 20 00 0f 85 d7 02 00 00 48 8b 43 10 48 89 dd 48 83 e8 10
RSP: 0018:ffff8880b3dc7920 EFLAGS: 00010a02
RAX: 1fe01ad80d18cd02 RBX: ff00d6c068c66800 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff868382d6 RDI: 0000000000000001
RBP: ffff88800015f400 R08: 0000000000000000 R09: fffffbfff15c8ff4
R10: ffffffff8ae47fa7 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880952e0340 R14: 0000000000000001 R15: ff00d6c068c66810
FS: 0000000000000000(0000) GS:ffff8880ba000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c02cead000 CR3: 000000003f3f2000 CR4: 00000000003426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: e8 b2 02 df fa callq 0xfadf02b9
7: 49 bc 00 00 00 00 00 movabs $0xdffffc0000000000,%r12
e: fc ff df
11: 44 8b 35 d1 0c 54 07 mov 0x7540cd1(%rip),%r14d # 0x7540ce9
18: eb 36 jmp 0x50
1a: e8 9a 02 df fa callq 0xfadf02b9
1f: 4c 8d 7b 10 lea 0x10(%rbx),%r15
23: 4c 89 f8 mov %r15,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1) <-- trapping instruction
2f: 0f 85 d7 02 00 00 jne 0x30c
35: 48 8b 43 10 mov 0x10(%rbx),%rax
39: 48 89 dd mov %rbx,%rbp
3c: 48 83 e8 10 sub $0x10,%rax


---
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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.