general protection fault in kernfs_kill_sb (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f0ab773f5c96 Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=140ce817800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fcce42b221691ff9
dashboard link: https://syzkaller.appspot.com/bug?extid=481ad819c717f6b78df9
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=15078e97800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12bf3697800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+481ad819c717f6b78df9@xxxxxxxxxxxxxxxxxxxxxxxxx

RBP: 00007ffc558bda60 R08: 0000000000000000 R09: 0000000300000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000004 R14: 0000000000001380 R15: 00007ffc558bd2f8
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4540 Comm: syz-executor884 Not tainted 4.17.0-rc4+ #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__list_del_entry_valid+0x84/0xf3 lib/list_debug.c:51
RSP: 0018:ffff8801aca6f860 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8801ac528498 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801ac5284a0
RBP: ffff8801aca6f878 R08: fffffbfff11cc855 R09: fffffbfff11cc854
R10: ffff8801aca6f878 R11: ffffffff88e642a7 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8801aca6f908 R15: ffff8801ac528498
FS:  0000000000f86880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004b6f3c CR3: 00000001d9730000 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]
 kernfs_kill_sb+0xa0/0x350 fs/kernfs/mount.c:361
 sysfs_kill_sb+0x22/0x40 fs/sysfs/mount.c:50
 deactivate_locked_super+0x97/0x100 fs/super.c:316
 kernfs_mount_ns+0x753/0x8e0 fs/kernfs/mount.c:335
 sysfs_mount+0xdf/0x200 fs/sysfs/mount.c:36
 mount_fs+0xae/0x328 fs/super.c:1267
 vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:1027 [inline]
 do_new_mount fs/namespace.c:2518 [inline]
 do_mount+0x564/0x3070 fs/namespace.c:2848
 ksys_mount+0x12d/0x140 fs/namespace.c:3064
 __do_sys_mount fs/namespace.c:3078 [inline]
 __se_sys_mount fs/namespace.c:3075 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4426a9
RSP: 002b:00007ffc558bd1b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004426a9
RDX: 00000000200000c0 RSI: 0000000020000080 RDI: 0000000020000040
RBP: 00007ffc558bda60 R08: 0000000000000000 R09: 0000000300000000
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000004 R14: 0000000000001380 R15: 00007ffc558bd2f8
Code: c5 0f 84 cc 00 00 00 48 b8 00 02 00 00 00 00 ad de 49 39 c4 0f 84 a5  
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 5f 49 8b 14 24 48 39 da 0f 85 ba 00 00 00 48 b8
RIP: __list_del_entry_valid+0x84/0xf3 lib/list_debug.c:51 RSP:  
ffff8801aca6f860
---[ end trace d148f307a34e229f ]---


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