general protection fault in kernfs_kill_sb

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 58b454eb Linux 4.14.112
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f8d3e3200000
kernel config: https://syzkaller.appspot.com/x/.config?x=8b0e7ab7678533ab
dashboard link: https://syzkaller.appspot.com/bug?extid=3c27271ea22f106cb9a9
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1686cd2d200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17ff8d5b200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3c2727...@syzkaller.appspotmail.com

RBP: 0000000000000003 R08: 0000000000000000 R09: 00007ffda6003331
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401da0
R13: 0000000000401e30 R14: 0000000000000000 R15: 0000000000000000
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7062 Comm: syz-executor621 Not tainted 4.14.112 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
task: ffff888089780200 task.stack: ffff888098758000
RIP: 0010:__list_del_entry_valid+0x85/0xf5 lib/list_debug.c:51
RSP: 0018:ffff88809875fae8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffffff891a91a0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88809208d820
RBP: ffff88809875fb00 R08: dffffc0000000000 R09: ffffffff88c7a240
R10: ffff88809875fb00 R11: ffff888089780200 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88809208d818 R15: ffff88809208d820
FS: 00000000017dd880(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000558b9a9fb190 CR3: 0000000092d8d000 CR4: 00000000001406f0
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]
kernfs_kill_sb+0x62/0x1e0 fs/kernfs/mount.c:365
cgroup_kill_sb+0xfb/0x330 kernel/cgroup/cgroup.c:2045
deactivate_locked_super+0x79/0xe0 fs/super.c:319
kernfs_mount_ns+0x629/0x790 fs/kernfs/mount.c:339
kernfs_mount include/linux/kernfs.h:543 [inline]
cgroup_do_mount+0x9e/0x420 kernel/cgroup/cgroup.c:1947
cgroup_mount+0x789/0x8b0 kernel/cgroup/cgroup.c:2014
mount_fs+0x9d/0x2a7 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
do_syscall_64+0x1eb/0x630 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4404b9
RSP: 002b:00007ffda6104b48 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffda6104b50 RCX: 00000000004404b9
RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000000000000 R09: 00007ffda6003331
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401da0
R13: 0000000000401e30 R14: 0000000000000000 R15: 0000000000000000
Code: c5 0f 84 e1 00 00 00 48 b8 00 02 00 00 00 00 ad de 49 39 c4 0f 84 e2
00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00
75 53 49 8b 14 24 4c 39 f2 0f 85 99 00 00 00 49 8d
RIP: __list_del_entry_valid+0x85/0xf5 lib/list_debug.c:51 RSP:
ffff88809875fae8
---[ end trace 367b5fb0e9c10504 ]---


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