Re: BUG: corrupted list in p9_read_work

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    0854ba5ff5c9 Merge git://git.kernel.org/pub/scm/linux/kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1514ec06400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=88e9a8a39dc0be2d
dashboard link: https://syzkaller.appspot.com/bug?extid=2222c34dc40b515f30dc
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10b91685400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2222c34dc40b515f30dc@xxxxxxxxxxxxxxxxxxxxxxxxx

FS-Cache: N-cookie d=000000000a092700 n=00000000d8ee0022
FS-Cache: N-key=[10] '34323935303034313132'
list_del corruption, ffff88019ae36ee8->next is LIST_POISON1  
(dead000000000100)
------------[ cut here ]------------
kobject: '9p-11043': free name
kernel BUG at lib/list_debug.c:47!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 2686 Comm: kworker/1:2 Not tainted 4.19.0-rc7+ #274
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
kobject: '9p-11049' (0000000096206f7a): kobject_add_internal:  
parent: 'bdi', set: 'devices'
Workqueue: events p9_read_work
RIP: 0010:__list_del_entry_valid.cold.1+0x26/0x58 lib/list_debug.c:45
Code: d7 fd 0f 0b 4c 89 e2 48 89 de 48 c7 c7 40 92 40 88 e8 7a a2 d7 fd 0f  
0b 4c 89 ea 48 89 de 48 c7 c7 e0 91 40 88 e8 66 a2 d7 fd <0f> 0b 48 89 de  
48 c7 c7 00 93 40 88 e8 55 a2 d7 fd 0f 0b 48 89 de
RSP: 0018:ffff8801cc5975b8 EFLAGS: 00010282
kobject: '9p-11049' (0000000096206f7a): kobject_uevent_env
RAX: 000000000000004e RBX: ffff88019ae36ee8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81650405 RDI: 0000000000000005
RBP: ffff8801cc5975d0 R08: ffff8801cc58a4c0 R09: ffffed003b5e4fe8
R10: ffffed003b5e4fe8 R11: ffff8801daf27f47 R12: dead000000000200
R13: dead000000000100 R14: ffff8801c8931050 R15: ffff8801c8931010
FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fef196c1000 CR3: 00000001ccff7000 CR4: 00000000001406e0
Call Trace:
kobject: '9p-11049' (0000000096206f7a): fill_kobj_path: path  
= '/devices/virtual/bdi/9p-11049'
 __list_del_entry include/linux/list.h:117 [inline]
 list_del include/linux/list.h:125 [inline]
 p9_read_work+0xab6/0x10e0 net/9p/trans_fd.c:379
kobject: 'loop4' (00000000513f3e2f): kobject_uevent_env
FS-Cache: Duplicate cookie detected
 process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
FS-Cache: O-cookie c=00000000911358e4 [p=000000006545c95d fl=222 nc=0 na=1]
FS-Cache: O-cookie d=000000000a092700 n=000000007635356b
FS-Cache: O-key=[10] '
34
32
39
35
30
30
34
31
32
 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
36
'
FS-Cache: N-cookie c=00000000abaeee81 [p=000000006545c95d fl=2 nc=0 na=1]
FS-Cache: N-cookie d=000000000a092700 n=00000000ee16a363
FS-Cache: N-key=[10] '
34
32
39
35
30
30
34
 kthread+0x35a/0x420 kernel/kthread.c:246
31
32
36
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
'
Modules linked in:
---[ end trace 41e06641f5c3c814 ]---
kobject: '9p-11050' (000000002a096aa2): kobject_add_internal:  
parent: 'bdi', set: 'devices'
RIP: 0010:__list_del_entry_valid.cold.1+0x26/0x58 lib/list_debug.c:45
Code: d7 fd 0f 0b 4c 89 e2 48 89 de 48 c7 c7 40 92 40 88 e8 7a a2 d7 fd 0f  
0b 4c 89 ea 48 89 de 48 c7 c7 e0 91 40 88 e8 66 a2 d7 fd <0f> 0b 48 89 de  
48 c7 c7 00 93 40 88 e8 55 a2 d7 fd 0f 0b 48 89 de
RSP: 0018:ffff8801cc5975b8 EFLAGS: 00010282
RAX: 000000000000004e RBX: ffff88019ae36ee8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81650405 RDI: 0000000000000005
RBP: ffff8801cc5975d0 R08: ffff8801cc58a4c0 R09: ffffed003b5e4fe8
R10: ffffed003b5e4fe8 R11: ffff8801daf27f47 R12: dead000000000200
R13: dead000000000100 R14: ffff8801c8931050 R15: ffff8801c8931010
FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fef196c1000 CR3: 00000001ccff7000 CR4: 00000000001406e0