[syzbot] general protection fault in path_init

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    49624efa65ac Merge tag 'denywrite-for-5.15' of git://githu..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1289787d300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=172cce3513a61f40
dashboard link: https://syzkaller.appspot.com/bug?extid=ae0fa0f86eb10f87db2d
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae0fa0f86eb10f87db2d@xxxxxxxxxxxxxxxxxxxxxxxxx

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 12334 Comm: iou-wrk-12330 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:path_init+0x8d/0x1920 fs/namei.c:2321
Code: 48 c1 ea 03 80 3c 02 00 0f 85 e7 15 00 00 48 8b 45 c8 48 8b 98 c0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 0f 85 b4 15 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc900019b77c0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81cac27f RDI: ffffc900019b7998
RBP: ffffc900019b7860 R08: 0000000000200000 R09: ffffc900019b7a98
R10: ffffffff81cac266 R11: 0000000000000024 R12: 0000000000000040
R13: ffffc900019b78d8 R14: ffffc900019b78d8 R15: ffffc900019b78d8
FS:  00007f8de3d0b700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8de3cea718 CR3: 000000008b11c000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 path_parentat+0x22/0x1c0 fs/namei.c:2504
 __filename_parentat+0x1bb/0x5a0 fs/namei.c:2527
 do_unlinkat+0xc4/0x650 fs/namei.c:4140
 io_unlinkat fs/io_uring.c:3703 [inline]
 io_issue_sqe+0x46c9/0x6ba0 fs/io_uring.c:6650
 io_wq_submit_work+0x1d4/0x300 fs/io_uring.c:6707
 io_worker_handle_work+0xcb1/0x1950 fs/io-wq.c:560
 io_wqe_worker+0x2cc/0xbb0 fs/io-wq.c:609
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Modules linked in:
---[ end trace 55738b1526c3e749 ]---
RIP: 0010:path_init+0x8d/0x1920 fs/namei.c:2321
Code: 48 c1 ea 03 80 3c 02 00 0f 85 e7 15 00 00 48 8b 45 c8 48 8b 98 c0 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 0f 85 b4 15 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc900019b77c0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81cac27f RDI: ffffc900019b7998
RBP: ffffc900019b7860 R08: 0000000000200000 R09: ffffc900019b7a98
R10: ffffffff81cac266 R11: 0000000000000024 R12: 0000000000000040
R13: ffffc900019b78d8 R14: ffffc900019b78d8 R15: ffffc900019b78d8
FS:  00007f8de3d0b700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc0711ca108 CR3: 000000008b11c000 CR4: 00000000001526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
----------------
Code disassembly (best guess):
   0:	48 c1 ea 03          	shr    $0x3,%rdx
   4:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   8:	0f 85 e7 15 00 00    	jne    0x15f5
   e:	48 8b 45 c8          	mov    -0x38(%rbp),%rax
  12:	48 8b 98 c0 00 00 00 	mov    0xc0(%rax),%rbx
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 da             	mov    %rbx,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 b4 15 00 00    	jne    0x15e8
  34:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  3b:	fc ff df
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b


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