Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 1 UID: 0 PID: 9635 Comm: syz.5.504 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:__umount_mnt+0x2ea/0x490
Code: 4c 89 f0 48 c1 e8 03 80 3c 28 00 74 08 4c 89 f7 e8 6b 87 e2 ff 4d 8b 3e 49 c7 06 00 00 00 00 4d 8d 77 18 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 48 87 e2 ff 49 83 3e 00 74 19 e8 0d
RSP: 0018:ffffc90004cd78a0 EFLAGS: 00010206
RAX: 0000000000000003 RBX: ffff88816b864008 RCX: ffff88810f3bd7c0
RDX: 0000000000000000 RSI: ffffc90004cd7960 RDI: ffff88816b864078
RBP: dffffc0000000000 R08: ffffffff8242a6dd R09: ffffffff8e416948
R10: 0000000000000000 R11: fffff5200099af0c R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000018 R15: 0000000000000000
FS:  00007f830fa9a6c0(0000) GS:ffff8882a945d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b323306eb CR3: 00000001766d2000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 mntput_no_expire_slowpath+0x950/0xbd0
 __fput+0x6bd/0xa70
 task_work_run+0x1d9/0x270
 do_exit+0x70f/0x23c0
 do_group_exit+0x21b/0x2d0
 get_signal+0x1284/0x1330
 arch_do_signal_or_restart+0xbc/0x830
 irqentry_exit+0x176/0x620
 asm_sysvec_call_function_single+0x1a/0x20
RIP: 0033:0x7f830ea53b13
Code: Unable to access opcode bytes at 0x7f830ea53ae9.
RSP: 002b:00007f830fa99470 EFLAGS: 00000206
RAX: 00000000000da148 RBX: 00007f830fa99530 RCX: 00000000000000ce
RDX: 0000000000001dff RSI: 0000000000000200 RDI: 00007f830fa995d0
RBP: 00000000000000e8 R08: 00007f8304800000 R09: 0000000000000000
R10: 0000200000012f42 R11: 00000000000097ae R12: 0000000000000181
R13: 00007f830ec52620 R14: 0000000000000011 R15: 00007f830fa995d0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__umount_mnt+0x2ea/0x490
Code: 4c 89 f0 48 c1 e8 03 80 3c 28 00 74 08 4c 89 f7 e8 6b 87 e2 ff 4d 8b 3e 49 c7 06 00 00 00 00 4d 8d 77 18 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 48 87 e2 ff 49 83 3e 00 74 19 e8 0d
RSP: 0018:ffffc90004cd78a0 EFLAGS: 00010206
RAX: 0000000000000003 RBX: ffff88816b864008 RCX: ffff88810f3bd7c0
RDX: 0000000000000000 RSI: ffffc90004cd7960 RDI: ffff88816b864078
RBP: dffffc0000000000 R08: ffffffff8242a6dd R09: ffffffff8e416948
R10: 0000000000000000 R11: fffff5200099af0c R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000018 R15: 0000000000000000
FS:  00007f830fa9a6c0(0000) GS:ffff8882a945d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b323306eb CR3: 00000001766d2000 CR4: 00000000000006f0
