BUG: corrupted list in p9_fd_cancelled

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: ee809c7e Linux 4.19.72
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=140f81a5600000
kernel config: https://syzkaller.appspot.com/x/.config?x=ad6c5c98f4231da9
dashboard link: https://syzkaller.appspot.com/bug?extid=587e1088976877f428ab
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16ac251a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+587e10...@syzkaller.appspotmail.com

FS-Cache: N-cookie d=00000000b1e1bdcc n=000000002808a3cc
FS-Cache: N-key=[10] '34323935313033393339'
9pnet: Insufficient options for proto=fd
list_del corruption, ffff8880817aa4b0->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: 4782 Comm: syz-executor.1 Not tainted 4.19.72 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45
Code: e8 45 f6 2f fe 0f 0b 4c 89 f6 48 c7 c7 20 4b 82 87 e8 34 f6 2f fe 0f
0b 4c 89 ea 4c 89 f6 48 c7 c7 60 4a 82 87 e8 20 f6 2f fe <0f> 0b 4c 89 e2
4c 89 f6 48 c7 c7 c0 4a 82 87 e8 0c f6 2f fe 0f 0b
RSP: 0018:ffff8880866f7698 EFLAGS: 00010286
RAX: 000000000000004e RBX: 1ffff11010cdeee1 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8155cf16 RDI: ffffed1010cdeec5
RBP: ffff8880866f76b0 R08: 000000000000004e R09: ffffed1015d25079
R10: ffffed1015d25078 R11: ffff8880ae9283c7 R12: dead000000000200
R13: dead000000000100 R14: ffff8880817aa4b0 R15: ffff8880817aa4b8
FS: 00007f7b679cd700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000046ef00 CR3: 000000009f48b000 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+0x3c/0x1c0 net/9p/trans_fd.c:725
p9_client_flush+0x1b7/0x1f0 net/9p/client.c:689
p9_client_rpc+0x101a/0x1220 net/9p/client.c:796
p9_client_version net/9p/client.c:967 [inline]
p9_client_create+0xb7f/0x1400 net/9p/client.c:1067
v9fs_session_init+0x1e7/0x18c0 fs/9p/v9fs.c:421
v9fs_mount+0x7d/0x920 fs/9p/vfs_super.c:135
mount_fs+0xa8/0x31f fs/super.c:1261
vfs_kern_mount.part.0+0x6f/0x410 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]
do_mount+0x53e/0x2bc0 fs/namespace.c:2799
ksys_mount+0xdb/0x150 fs/namespace.c:3015
__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3026
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4598e9
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f7b679ccc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004598e9
RDX: 0000000020000180 RSI: 0000000020000140 RDI: 0000000000000000
RBP: 000000000075bf20 R08: 0000000020000380 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7b679cd6d4
R13: 00000000004c5e68 R14: 00000000004da9b0 R15: 00000000ffffffff
Modules linked in:
---[ end trace df6b5b7310d0f624 ]---
RIP: 0010:__list_del_entry_valid.cold+0x23/0x4f lib/list_debug.c:45
kobject: 'loop4' (000000002d2f7587): kobject_uevent_env
Code: e8 45 f6 2f fe 0f 0b 4c 89 f6 48 c7 c7 20 4b 82 87 e8 34 f6 2f fe 0f
0b 4c 89 ea 4c 89 f6 48 c7 c7 60 4a 82 87 e8 20 f6 2f fe <0f> 0b 4c 89 e2
4c 89 f6 48 c7 c7 c0 4a 82 87 e8 0c f6 2f fe 0f 0b
RSP: 0018:ffff8880866f7698 EFLAGS: 00010286
kobject: 'loop4' (000000002d2f7587): fill_kobj_path: path
= '/devices/virtual/block/loop4'
RAX: 000000000000004e RBX: 1ffff11010cdeee1 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8155cf16 RDI: ffffed1010cdeec5
RBP: ffff8880866f76b0 R08: 000000000000004e R09: ffffed1015d25079
R10: ffffed1015d25078 R11: ffff8880ae9283c7 R12: dead000000000200
R13: dead000000000100 R14: ffff8880817aa4b0 R15: ffff8880817aa4b8
FS: 00007f7b679cd700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000046ef00 CR3: 000000009f48b000 CR4: 00000000001406e0
kobject: 'loop2' (000000003eb7e877): kobject_uevent_env
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 78a917bea6ede80a0635a4fb4f87d713bb6fbeb1
Author: Alexander Shishkin <alexander...@linux.intel.com>
Date: Tue Nov 5 07:57:02 2019 +0000

perf/core: Consistently fail fork on allocation failures

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=132d7049e00000
start commit: ee809c7e Linux 4.19.72
git tree: linux-4.19.y

kernel config: https://syzkaller.appspot.com/x/.config?x=ad6c5c98f4231da9
dashboard link: https://syzkaller.appspot.com/bug?extid=587e1088976877f428ab

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16ac251a600000

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

#syz fix: perf/core: Consistently fail fork on allocation failures

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