general protection fault in locks_remove_flock

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    d881de30d29e Add linux-next specific files for 20181107
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1594d983400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=caa433e1c8778437
dashboard link: https://syzkaller.appspot.com/bug?extid=2400c924363a9a43d116
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2400c924363a9a43d116@xxxxxxxxxxxxxxxxxxxxxxxxx

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: 13218 Comm: syz-executor3 Not tainted 4.20.0-rc1-next-20181107+  
#107
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:locks_remove_flock+0x216/0x350 fs/locks.c:2567
Code: 00 0f 85 3a 01 00 00 48 8b 5b 98 48 85 db 74 3a e8 1f 41 92 ff 48 8d  
7b 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 17 01 00 00 48 8b 5b 08 48 85 db 74 0d e8 f2 40
RSP: 0018:ffff8801895a7880 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000041b58ab3 RCX: ffffffff81ed555d
RDX: 000000000836b157 RSI: ffffffff81ed5c71 RDI: 0000000041b58abb
RBP: ffff8801895a7a60 R08: ffff880194096140 R09: ffffed003b5c5b67
R10: ffffed003b5c5b67 R11: ffff8801dae2db3b R12: ffff8801cb266ac0
R13: ffff8801895a78f8 R14: 1ffff100312b4f13 R15: dffffc0000000000
FS:  0000000002927940(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000400200 CR3: 00000001bd0d5000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 locks_remove_file+0x148/0x5c0 fs/locks.c:2607
 __fput+0x2f0/0xa70 fs/file_table.c:271
 ____fput+0x15/0x20 fs/file_table.c:312
 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x411021
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 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:00007ffe309feb50 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000411021
RDX: 0000000000000000 RSI: 0000000000730420 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00007ffe309fea70 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000001 R14: 000000000000010d R15: 0000000000000003
Modules linked in:
---[ end trace 69f886046d36502a ]---
RIP: 0010:locks_remove_flock+0x216/0x350 fs/locks.c:2567
kasan: CONFIG_KASAN_INLINE enabled
Code: 00 0f 85 3a 01 00 00 48 8b 5b 98 48 85 db 74 3a e8 1f 41 92 ff 48 8d  
7b 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
85 17 01 00 00 48 8b 5b 08 48 85 db 74 0d e8 f2 40
kasan: GPF could be caused by NULL-ptr deref or user memory access
RSP: 0018:ffff8801895a7880 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000041b58ab3 RCX: ffffffff81ed555d
kasan: CONFIG_KASAN_INLINE enabled
RDX: 000000000836b157 RSI: ffffffff81ed5c71 RDI: 0000000041b58abb
RBP: ffff8801895a7a60 R08: ffff880194096140 R09: ffffed003b5c5b67
R10: ffffed003b5c5b67 R11: ffff8801dae2db3b R12: ffff8801cb266ac0
kasan: GPF could be caused by NULL-ptr deref or user memory access
R13: ffff8801895a78f8 R14: 1ffff100312b4f13 R15: dffffc0000000000
FS:  0000000002927940(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000072c000 CR3: 00000001bd0d5000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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