Re: general protection fault in prepare_to_wait

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    23e93c9b2cde Revert "gfs2: read journal in large chunks to..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14e94014c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ee434566c893c7b1
dashboard link: https://syzkaller.appspot.com/bug?extid=55f9d3e51d49e20b2ce5
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=109c886cc00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11ed20d0c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+55f9d3e51d49e20b2ce5@xxxxxxxxxxxxxxxxxxxxxxxxx

IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_hsr: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_0: link becomes ready
kasan: CONFIG_KASAN_INLINE enabled
8021q: adding VLAN 0 to HW filter on device batadv0
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7785 Comm: syz-executor295 Not tainted 5.0.0-rc6+ #72
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__lock_acquire+0x8df/0x4700 kernel/locking/lockdep.c:3215
Code: 28 00 00 00 0f 85 35 27 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f  
5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f  
85 dc 27 00 00 49 81 3c 24 20 25 9a 89 0f 84 03 f8
RSP: 0018:ffff888094c6f970 EFLAGS: 00010006
kobject: 'vlan0' (00000000d30c60ff): kobject_add_internal: parent: 'mesh',  
set: '<NULL>'
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000018
RBP: ffff888094c6fb40 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000018
R13: 0000000000000001 R14: 0000000000000000 R15: ffff88808c0f00c0
FS:  00007f9abeeec700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
8021q: adding VLAN 0 to HW filter on device batadv0
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kobject: 'vlan0' (00000000a54e32cc): kobject_add_internal: parent: 'mesh',  
set: '<NULL>'
CR2: 00000000004d0910 CR3: 00000000906d2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
8021q: adding VLAN 0 to HW filter on device batadv0
Call Trace:
kobject: 'vlan0' (0000000016be0e34): kobject_add_internal: parent: 'mesh',  
set: '<NULL>'
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
 prepare_to_wait+0x7c/0x300 kernel/sched/wait.c:230
 nr_accept+0x239/0x790 net/netrom/af_netrom.c:796
 __sys_accept4+0x350/0x6a0 net/socket.c:1588
 __do_sys_accept net/socket.c:1629 [inline]
 __se_sys_accept net/socket.c:1626 [inline]
 __x64_sys_accept+0x75/0xb0 net/socket.c:1626
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x449489
Code: e8 7c e6 ff ff 48 83 c4 18 c3 0f 1f 80 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 0f 83 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9abeeebcc8 EFLAGS: 00000246 ORIG_RAX: 000000000000002b
RAX: ffffffffffffffda RBX: 00000000006dfc68 RCX: 0000000000449489
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000006dfc60 R08: 00007f9abeeec700 R09: 0000000000000000
R10: 00007f9abeeec700 R11: 0000000000000246 R12: 00000000006dfc6c
R13: 00007ffe8979730f R14: 00007f9abeeec9c0 R15: 0000000000000002
Modules linked in:
---[ end trace 91ccd60fc619e2e6 ]---
RIP: 0010:__lock_acquire+0x8df/0x4700 kernel/locking/lockdep.c:3215
Code: 28 00 00 00 0f 85 35 27 00 00 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f  
5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f  
85 dc 27 00 00 49 81 3c 24 20 25 9a 89 0f 84 03 f8
RSP: 0018:ffff888094c6f970 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000018
RBP: ffff888094c6fb40 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000018
R13: 0000000000000001 R14: 0000000000000000 R15: ffff88808c0f00c0
FS:  00007f9abeeec700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004d0910 CR3: 00000000906d2000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400