Subject: Re: [syzbot] WARNING: locking bug in inet_autobind

From: syzbot <[email-masked]>
Date: Wed, 28 Dec 2022 22:26:36 -0800

syzbot has found a reproducer for the following issue on:

HEAD commit:    1b929c02afd3 Linux 6.2-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=145c6a68480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2651619a26b4d687
dashboard link: https://syzkaller.appspot.com/bug?extid=94cc2a66fc228b23f360
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=13e13e32480000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13790f08480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d1849f1ca322/disk-1b929c02.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/924cb8aa4ada/vmlinux-1b929c02.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8c7330dae0a0/bzImage-1b929c02.xz

The issue was bisected to:

commit c0d9271ecbd891cdeb0fad1edcdd99ee717a655f
Author: Yong Zhao <[email-masked]>
Date:   Fri Feb 1 23:36:21 2019 +0000

    drm/amdgpu: Delete user queue doorbell variables

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1433ece4a00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1633ece4a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1233ece4a00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: c0d9271ecbd8 ("drm/amdgpu: Delete user queue doorbell variables")

------------[ cut here ]------------
Looking for class "l2tp_sock" with key l2tp_socket_class, but found a different class "slock-AF_INET6" with the same key
WARNING: CPU: 0 PID: 7280 at kernel/locking/lockdep.c:937 look_up_lock_class+0x97/0x110 kernel/locking/lockdep.c:937
Modules linked in:
CPU: 0 PID: 7280 Comm: syz-executor835 Not tainted 6.2.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:look_up_lock_class+0x97/0x110 kernel/locking/lockdep.c:937
Code: 17 48 81 fa e0 e5 f6 8f 74 59 80 3d 5d bc 57 04 00 75 50 48 c7 c7 00 4d 4c 8a 48 89 04 24 c6 05 49 bc 57 04 01 e8 a9 42 b9 ff <0f> 0b 48 8b 04 24 eb 31 9c 5a 80 e6 02 74 95 e8 45 38 02 fa 85 c0
RSP: 0018:ffffc9000b5378b8 EFLAGS: 00010082
RAX: 0000000000000000 RBX: ffffffff91c06a00 RCX: 0000000000000000
RDX: ffff8880292d0000 RSI: ffffffff8166721c RDI: fffff520016a6f09
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000201 R11: 20676e696b6f6f4c R12: 0000000000000000
R13: ffff88802a5820b0 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f1fd7a97700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000100 CR3: 0000000078ab4000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 register_lock_class+0xbe/0x1120 kernel/locking/lockdep.c:1289
 __lock_acquire+0x109/0x56d0 kernel/locking/lockdep.c:4934
 lock_acquire kernel/locking/lockdep.c:5668 [inline]
 lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:355 [inline]
 lock_sock_nested+0x5f/0xf0 net/core/sock.c:3473
 lock_sock include/net/sock.h:1725 [inline]
 inet_autobind+0x1a/0x190 net/ipv4/af_inet.c:177
 inet_send_prepare net/ipv4/af_inet.c:813 [inline]
 inet_send_prepare+0x325/0x4e0 net/ipv4/af_inet.c:807
 inet6_sendmsg+0x43/0xe0 net/ipv6/af_inet6.c:655
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xd3/0x120 net/socket.c:734
 __sys_sendto+0x23a/0x340 net/socket.c:2117
 __do_sys_sendto net/socket.c:2129 [inline]
 __se_sys_sendto net/socket.c:2125 [inline]
 __x64_sys_sendto+0xe1/0x1b0 net/socket.c:2125
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f1fd78538b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1fd7a971f8 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f1fd78f0038 RCX: 00007f1fd78538b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f1fd78f0030 R08: 0000000020000100 R09: 000000000000001c
R10: 0000000004008000 R11: 0000000000000212 R12: 00007f1fd78f003c
R13: 00007f1fd79ffc8f R14: 00007f1fd7a97300 R15: 0000000000022000
 </TASK>