BUG: corrupted list in p9_read_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    37b5dca2898d Merge tag 'rtc-4.18-2' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b3e770400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=25856fac4e580aa7
dashboard link: https://syzkaller.appspot.com/bug?extid=2222c34dc40b515f30dc
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+2222c34dc40b515f30dc@xxxxxxxxxxxxxxxxxxxxxxxxx

list_del corruption, ffff8801931d8e28->next is LIST_POISON1  
(dead000000000100)
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:47!
invalid opcode: 0000 [#1] SMP KASAN
CPU: 0 PID: 27 Comm: kworker/0:2 Not tainted 4.18.0-rc4+ #148
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events p9_read_work
RIP: 0010:__list_del_entry_valid.cold.1+0x26/0x58 lib/list_debug.c:45
Code: 02 fe 0f 0b 4c 89 e2 48 89 de 48 c7 c7 60 68 1a 88 e8 ba 69 02 fe 0f  
0b 4c 89 ea 48 89 de 48 c7 c7 00 68 1a 88 e8 a6 69 02 fe <0f> 0b 48 89 de  
48 c7 c7 20 69 1a 88 e8 95 69 02 fe 0f 0b 48 89 de
RSP: 0018:ffff8801d94575b0 EFLAGS: 00010286
RAX: 000000000000004e RBX: ffff8801931d8e28 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81631821 RDI: 0000000000000001
RBP: ffff8801d94575c8 R08: ffff8801d9448700 R09: ffffed003b5c4fc0
R10: ffffed003b5c4fc0 R11: ffff8801dae27e07 R12: dead000000000200
R13: dead000000000100 R14: ffff8801931d8e00 R15: ffff8801996f7a10
FS:  0000000000000000(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9e4e7e0000 CR3: 00000001aeeae000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __list_del_entry include/linux/list.h:117 [inline]
 list_del include/linux/list.h:125 [inline]
 p9_read_work+0xa29/0x1060 net/9p/trans_fd.c:375
 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace 4e7d7b3b542c6c1e ]---
RIP: 0010:__list_del_entry_valid.cold.1+0x26/0x58 lib/list_debug.c:45
Code: 02 fe 0f 0b 4c 89 e2 48 89 de 48 c7 c7 60 68 1a 88 e8 ba 69 02 fe 0f  
0b 4c 89 ea 48 89 de 48 c7 c7 00 68 1a 88 e8 a6 69 02 fe <0f> 0b 48 89 de  
48 c7 c7 20 69 1a 88 e8 95 69 02 fe 0f 0b 48 89 de
RSP: 0018:ffff8801d94575b0 EFLAGS: 00010286
RAX: 000000000000004e RBX: ffff8801931d8e28 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81631821 RDI: 0000000000000001
RBP: ffff8801d94575c8 R08: ffff8801d9448700 R09: ffffed003b5c4fc0
R10: ffffed003b5c4fc0 R11: ffff8801dae27e07 R12: dead000000000200
R13: dead000000000100 R14: ffff8801931d8e00 R15: ffff8801996f7a10
FS:  0000000000000000(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9e4e7e0000 CR3: 00000001aeeae000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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