general protection fault in wb_workfn (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    305bb5521282 Merge tag 'selinux-pr-20180516' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153eb40f800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f3b4e30da84ec1ed
dashboard link: https://syzkaller.appspot.com/bug?extid=4a7438e774b21ddd8eca
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+4a7438e774b21ddd8eca@xxxxxxxxxxxxxxxxxxxxxxxxx

binder: 13169:13171 ioctl 40047459 20000000 returned -22
sock: process `syz-executor6' is using obsolete setsockopt SO_BSDCOMPAT
binder: 13169:13202 Acquire 1 refcount change on invalid ref 0 ret -22
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 88 Comm: kworker/u4:3 Not tainted 4.17.0-rc5+ #55
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: writeback wb_workfn
RIP: 0010:dev_name include/linux/device.h:1008 [inline]
RIP: 0010:wb_workfn+0x195/0x1740 fs/fs-writeback.c:1937
RSP: 0018:ffff8801d964f270 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff814e0f15
RDX: 000000000000000a RSI: ffffffff81cd221d RDI: 0000000000000050
RBP: ffff8801d964f750 R08: ffff8801d97c6700 R09: ffffed003b5e46c2
R10: ffffed003b5e46c2 R11: ffff8801daf23613 R12: 0000000000000001
R13: 1ffff1003b2c9f37 R14: ffff8801d964f728 R15: ffff8801d6836f18
FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fec3a840db8 CR3: 00000001b49ae000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
 process_scheduled_works kernel/workqueue.c:2205 [inline]
 worker_thread+0xa30/0x1440 kernel/workqueue.c:2284
 kthread+0x345/0x410 kernel/kthread.c:240
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Code: fa 48 c1 ea 03 80 3c 02 00 0f 85 ee 13 00 00 48 8b 9b 08 06 00 00 48  
b8 00 00 00 00 00 fc ff df 48 8d 7b 50 48 89 fa 48 c1 ea 03 <80> 3c 02 00  
0f 85 3f 14 00 00 4c 8b 63 50 4d 85 e4 0f 84 a9 0e
RIP: dev_name include/linux/device.h:1008 [inline] RSP: ffff8801d964f270
RIP: wb_workfn+0x195/0x1740 fs/fs-writeback.c:1937 RSP: ffff8801d964f270
---[ end trace baf4ced88bb756b8 ]---


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