BUG: corrupted list in p9_read_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 43598c57 Linux 4.14.156
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14ae7696e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=20cdce6bea3c2570
dashboard link: https://syzkaller.appspot.com/bug?extid=cfb2d54d40b2cef84c78
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16acce7ee00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+cfb2d5...@syzkaller.appspotmail.com

list_del corruption, ffff888048f4b428->next is LIST_POISON1
(dead000000000100)
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:45!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
kobject: 'loop3' (ffff8880a410e4a0): kobject_uevent_env
Modules linked in:
CPU: 1 PID: 7020 Comm: kworker/1:1 Not tainted 4.14.156-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events p9_read_work
kobject: 'loop3' (ffff8880a410e4a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
task: ffff8880a4db0700 task.stack: ffff888087340000
RIP: 0010:__list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45
RSP: 0018:ffff888087347c70 EFLAGS: 00010286
kobject: 'loop1' (ffff8880a406d4e0): kobject_uevent_env
RAX: 000000000000004e RBX: ffff888048f4b400 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff86ac2f80 RDI: ffffed1010e68f84
RBP: ffff888087347c88 R08: 000000000000004e R09: ffff8880a4db0ff0
R10: 0000000000000000 R11: 0000000000000000 R12: dead000000000200
R13: dead000000000100 R14: ffff888048f4b428 R15: 0000000000000004
FS: 0000000000000000(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000a3850000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kobject: 'loop1' (ffff8880a406d4e0): fill_kobj_path: path
= '/devices/virtual/block/loop1'
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+0x833/0xd80 net/9p/trans_fd.c:386
kobject: 'loop3' (ffff8880a410e4a0): kobject_uevent_env
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
kobject: 'loop3' (ffff8880a410e4a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
kobject: 'loop3' (ffff8880a410e4a0): kobject_uevent_env
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code:
kobject: 'loop3' (ffff8880a410e4a0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
e6 e8 14 ad 40 fe 0f 0b 4c 89 f6 48 c7 c7 e0 fb e3 86 e8 03 ad 40 fe
kobject: 'loop0' (ffff8880a4024be0): kobject_uevent_env
0f 0b 4c 89 ea 4c 89 f6 48 c7 c7 20 fb e3 86 e8 ef ac 40 fe <0f> 0b 4c 89
e2 4c 89 f6 48 c7 c7 80
kobject: 'loop0' (ffff8880a4024be0): fill_kobj_path: path
= '/devices/virtual/block/loop0'
fb e3 86 e8 db ac 40 fe 0f
RIP: __list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45 RSP:
ffff888087347c70
---[ end trace a8b4fa7dd6fe9a14 ]---
kobject: 'loop1' (ffff8880a406d4e0): kobject_uevent_env


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