syzbot

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000023: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
CPU: 0 UID: 0 PID: 6414 Comm: syz.3.69 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:mntput+0x31/0xc0 fs/namespace.c:1430
Code: 41 56 41 54 53 48 89 fb e8 1c da 7e ff 48 85 db 74 47 49 bf 00 00 00 00 00 fc ff df 4c 8d b3 24 01 00 00 4d 89 f4 49 c1 ec 03 <43> 0f b6 04 3c 84 c0 75 50 48 83 c3 e0 41 8b 2e 31 ff 89 ee e8 26
RSP: 0018:ffffc9000462fd90 EFLAGS: 00010202
RAX: ffffffff8242c664 RBX: fffffffffffffff4 RCX: ffff888077aa5b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffff4
RBP: ffffc9000462fed0 R08: ffff888077aa5b87 R09: 1ffff1100ef54b70
R10: dffffc0000000000 R11: ffffed100ef54b71 R12: 0000000000000023
R13: dffffc0000000000 R14: 0000000000000118 R15: dffffc0000000000
FS:  00007fdf2c77f6c0(0000) GS:ffff888125e8b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555575df7808 CR3: 0000000076002000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __do_sys_fsmount fs/namespace.c:4380 [inline]
 __se_sys_fsmount+0x893/0xa90 fs/namespace.c:4279
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdf2b98f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdf2c77f038 EFLAGS: 00000246 ORIG_RAX: 00000000000001b0
RAX: ffffffffffffffda RBX: 00007fdf2bbe6180 RCX: 00007fdf2b98f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fdf2ba13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdf2bbe6218 R14: 00007fdf2bbe6180 R15: 00007ffd8048bbc8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mntput+0x31/0xc0 fs/namespace.c:1430
Code: 41 56 41 54 53 48 89 fb e8 1c da 7e ff 48 85 db 74 47 49 bf 00 00 00 00 00 fc ff df 4c 8d b3 24 01 00 00 4d 89 f4 49 c1 ec 03 <43> 0f b6 04 3c 84 c0 75 50 48 83 c3 e0 41 8b 2e 31 ff 89 ee e8 26
RSP: 0018:ffffc9000462fd90 EFLAGS: 00010202
RAX: ffffffff8242c664 RBX: fffffffffffffff4 RCX: ffff888077aa5b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffff4
RBP: ffffc9000462fed0 R08: ffff888077aa5b87 R09: 1ffff1100ef54b70
R10: dffffc0000000000 R11: ffffed100ef54b71 R12: 0000000000000023
R13: dffffc0000000000 R14: 0000000000000118 R15: dffffc0000000000
FS:  00007fdf2c77f6c0(0000) GS:ffff888125f8b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd4a51d5e8 CR3: 0000000076002000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	41 56                	push   %r14
   2:	41 54                	push   %r12
   4:	53                   	push   %rbx
   5:	48 89 fb             	mov    %rdi,%rbx
   8:	e8 1c da 7e ff       	call   0xff7eda29
   d:	48 85 db             	test   %rbx,%rbx
  10:	74 47                	je     0x59
  12:	49 bf 00 00 00 00 00 	movabs $0xdffffc0000000000,%r15
  19:	fc ff df
  1c:	4c 8d b3 24 01 00 00 	lea    0x124(%rbx),%r14
  23:	4d 89 f4             	mov    %r14,%r12
  26:	49 c1 ec 03          	shr    $0x3,%r12
* 2a:	43 0f b6 04 3c       	movzbl (%r12,%r15,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	75 50                	jne    0x83
  33:	48 83 c3 e0          	add    $0xffffffffffffffe0,%rbx
  37:	41 8b 2e             	mov    (%r14),%ebp
  3a:	31 ff                	xor    %edi,%edi
  3c:	89 ee                	mov    %ebp,%esi
  3e:	e8                   	.byte 0xe8
  3f:	26                   	es