BUG: corrupted list in p9_fd_cancelled

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b98aebd2 Linux 4.14.150
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14c5797f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=c52c93b368dac5a7
dashboard link: https://syzkaller.appspot.com/bug?extid=4223d5758fb837a10a31
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131abf6f600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4223d5...@syzkaller.appspotmail.com

9pnet: Insufficient options for proto=fd
list_del corruption, ffff88804ebebda8->next is LIST_POISON1
(dead000000000100)
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:45!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 25265 Comm: syz-executor.1 Not tainted 4.14.150 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff88809b73c140 task.stack: ffff88804eac8000
RIP: 0010:__list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45
kobject: 'loop0' (ffff8880a492eee0): kobject_uevent_env
RSP: 0018:ffff88804eacf780 EFLAGS: 00010286
RAX: 000000000000004e RBX: ffff88804ebebd80 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff866d10e0 RDI: ffffed1009d59ee6
RBP: ffff88804eacf798 R08: 000000000000004e R09: ffff88809b73c9e0
R10: 0000000000000000 R11: 0000000000000000 R12: dead000000000200
R13: dead000000000100 R14: ffff88804ebebda8 R15: ffff88804ebebdf0
FS: 00007f4d7ae56700(0000) GS:ffff8880aef00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000009e5a8000 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_fd_cancelled+0x34/0x190 net/9p/trans_fd.c:719
p9_client_flush+0x1b5/0x210 net/9p/client.c:698
p9_client_rpc+0xf12/0x1180 net/9p/client.c:807
kobject: 'loop0' (ffff8880a492eee0): fill_kobj_path: path
= '/devices/virtual/block/loop0'
p9_client_version net/9p/client.c:980 [inline]
p9_client_create+0x997/0x1120 net/9p/client.c:1088
v9fs_session_init+0x1dc/0x1620 fs/9p/v9fs.c:422
kobject: 'loop3' (ffff8880a4a189e0): kobject_uevent_env
v9fs_mount+0x7d/0x870 fs/9p/vfs_super.c:135
mount_fs+0x97/0x2a1 fs/super.c:1237
vfs_kern_mount.part.0+0x5e/0x3d0 fs/namespace.c:1046
vfs_kern_mount fs/namespace.c:1036 [inline]
do_new_mount fs/namespace.c:2549 [inline]
do_mount+0x417/0x27d0 fs/namespace.c:2879
SYSC_mount fs/namespace.c:3095 [inline]
SyS_mount+0xab/0x120 fs/namespace.c:3072
kobject: 'loop3' (ffff8880a4a189e0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459a59
RSP: 002b:00007f4d7ae55c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459a59
RDX: 0000000020000100 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000075bf20 R08: 0000000020000600 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4d7ae566d4
R13: 00000000004c6252 R14: 00000000004db3a8 R15: 00000000ffffffff
Code: e6 e8 94 c2 72
kobject: 'loop3' (ffff8880a4a189e0): kobject_uevent_env
fe
kobject: 'loop3' (ffff8880a4a189e0): fill_kobj_path: path
= '/devices/virtual/block/loop3'
0f 0b 4c 89 f6 48 c7 c7 80 35 9d 86 e8 83 c2 72 fe 0f 0b 4c 89 ea 4c 89 f6
48 c7 c7 c0 34 9d 86 e8 6f c2 72 fe <0f> 0b 4c 89 e2 4c 89 f6 48 c7 c7 20
35 9d 86 e8 5b c2 72
kobject: 'loop0' (ffff8880a492eee0): kobject_uevent_env
fe 0f
RIP: __list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45 RSP:
ffff88804eacf780
---[ end trace 0146b3a2a12e67c7 ]---
kobject: 'loop0' (ffff8880a492eee0): fill_kobj_path: path
= '/devices/virtual/block/loop0'


---
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[syzbot]

syzbot suspects this bug was fixed by commit:

commit 8a82aee7bdfd5bfcabdc741b1051dae98b576f9c
Author: Suzuki K Poulose <suzuki....@arm.com>
Date: Thu Oct 24 12:48:12 2019 +0000

arm64: Add MIDR encoding for Arm Cortex-A55 and Cortex-A35

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1217bac6e00000
start commit: b98aebd2 Linux 4.14.150
git tree: linux-4.14.y

kernel config: https://syzkaller.appspot.com/x/.config?x=c52c93b368dac5a7
dashboard link: https://syzkaller.appspot.com/bug?extid=4223d5758fb837a10a31

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131abf6f600000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: arm64: Add MIDR encoding for Arm Cortex-A55 and Cortex-A35

For information about bisection process see: https://goo.gl/tpsmEJ#bisection