BUG: corrupted list in p9_read_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c3038e71 Linux 4.19.80
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10edba37600000
kernel config: https://syzkaller.appspot.com/x/.config?x=44c623b7e5432cee
dashboard link: https://syzkaller.appspot.com/bug?extid=56fb89065f70cacfbd9a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1238ca60e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+56fb89...@syzkaller.appspotmail.com

9pnet: Insufficient options for proto=fd
9pnet: Insufficient options for proto=fd
list_del corruption, ffff888098d8acb0->next is LIST_POISON1
(dead000000000100)
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:45!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 13580 Comm: kworker/1:0 Not tainted 4.19.80 #0
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+0x23/0x4f lib/list_debug.c:45
Code: e8 35 1a 31 fe 0f 0b 4c 89 f6 48 c7 c7 e0 3f 82 87 e8 24 1a 31 fe 0f
0b 4c 89 ea 4c 89 f6 48 c7 c7 20 3f 82 87 e8 10 1a 31 fe <0f> 0b 4c 89 e2
4c 89 f6 48 c7 c7 80 3f 82 87 e8 fc 19 31 fe 0f 0b
RSP: 0018:ffff888083dcfc48 EFLAGS: 00010286
RAX: 000000000000004e RBX: ffff888098d8ac00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81553f06 RDI: ffffed10107b9f7b
RBP: ffff888083dcfc60 R08: 000000000000004e R09: ffffed1015d25079
R10: ffffed1015d25078 R11: ffff8880ae9283c7 R12: dead000000000200
R13: dead000000000100 R14: ffff888098d8acb0 R15: ffff888098d8acb0
FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
9pnet: Insufficient options for proto=fd
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fffbc8de4d9 CR3: 000000008a8d0000 CR4: 00000000001406e0
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+0x9e5/0x1050 net/9p/trans_fd.c:378
process_one_work+0x989/0x1750 kernel/workqueue.c:2153
worker_thread+0x98/0xe40 kernel/workqueue.c:2296
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Modules linked in:
---[ end trace 491f9057387148a6 ]---
RIP: 0010:__list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45
Code: e8 35 1a 31 fe 0f 0b 4c 89 f6 48 c7 c7 e0 3f 82 87 e8 24 1a 31 fe 0f
0b 4c 89 ea 4c 89 f6 48 c7 c7 20 3f 82 87 e8 10 1a 31 fe <0f> 0b 4c 89 e2
4c 89 f6 48 c7 c7 80 3f 82 87 e8 fc 19 31 fe 0f 0b
kobject: 'loop0' (000000003e27d849): kobject_uevent_env
RSP: 0018:ffff888083dcfc48 EFLAGS: 00010286
RAX: 000000000000004e RBX: ffff888098d8ac00 RCX: 0000000000000000
kobject: 'loop0' (000000003e27d849): fill_kobj_path: path
= '/devices/virtual/block/loop0'
RDX: 0000000000000000 RSI: ffffffff81553f06 RDI: ffffed10107b9f7b
kobject: 'loop4' (000000005f191186): kobject_uevent_env
RBP: ffff888083dcfc60 R08: 000000000000004e R09: ffffed1015d25079
R10: ffffed1015d25078 R11: ffff8880ae9283c7 R12: dead000000000200
R13: dead000000000100 R14: ffff888098d8acb0 R15: ffff888098d8acb0
FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fffbc8de4d9 CR3: 000000008a8d0000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kobject: 'loop4' (000000005f191186): fill_kobj_path: path
= '/devices/virtual/block/loop4'
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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