[syzbot] general protection fault in do_xmote

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c3e0e1e23c70 Merge tag 'irq_urgent_for_v6.0' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11664a70880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a1992c90769e07
dashboard link: https://syzkaller.appspot.com/bug?extid=ececff266234ba40fe13
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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+ececff266234ba40fe13@xxxxxxxxxxxxxxxxxxxxxxxxx

general protection fault, probably for non-canonical address 0xdffffc0000000097: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000004b8-0x00000000000004bf]
CPU: 2 PID: 70 Comm: kworker/2:1H Not tainted 6.0.0-rc7-syzkaller-00081-gc3e0e1e23c70 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Workqueue: glock_workqueue glock_work_func
RIP: 0010:is_system_glock fs/gfs2/glock.c:720 [inline]
RIP: 0010:do_xmote+0x492/0xc40 fs/gfs2/glock.c:828
Code: 03 80 3c 02 00 0f 85 2f 07 00 00 4d 8b ad 18 07 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bd b8 04 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 ed 06 00 00 49 3b ad b8 04 00 00 0f 84 77 05 00
RSP: 0018:ffffc90000aa7c50 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff888027624000 RCX: 0000000000000000
RDX: 0000000000000097 RSI: ffffffff8381e370 RDI: 00000000000004b8
RBP: ffff888074ceea90 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888074ceeaf8 R15: ffff888074ceeab0
FS:  0000000000000000(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000990140 CR3: 0000000076461000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 run_queue+0x3cf/0x660 fs/gfs2/glock.c:893
 glock_work_func+0xbe/0x3a0 fs/gfs2/glock.c:1059
 process_one_work+0x991/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:is_system_glock fs/gfs2/glock.c:720 [inline]
RIP: 0010:do_xmote+0x492/0xc40 fs/gfs2/glock.c:828
Code: 03 80 3c 02 00 0f 85 2f 07 00 00 4d 8b ad 18 07 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bd b8 04 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 ed 06 00 00 49 3b ad b8 04 00 00 0f 84 77 05 00
RSP: 0018:ffffc90000aa7c50 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff888027624000 RCX: 0000000000000000
RDX: 0000000000000097 RSI: ffffffff8381e370 RDI: 00000000000004b8
RBP: ffff888074ceea90 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888074ceeaf8 R15: ffff888074ceeab0
FS:  0000000000000000(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000990140 CR3: 0000000076461000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   4:	0f 85 2f 07 00 00    	jne    0x739
   a:	4d 8b ad 18 07 00 00 	mov    0x718(%r13),%r13
  11:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  18:	fc ff df
  1b:	49 8d bd b8 04 00 00 	lea    0x4b8(%r13),%rdi
  22:	48 89 fa             	mov    %rdi,%rdx
  25:	48 c1 ea 03          	shr    $0x3,%rdx
* 29:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2d:	0f 85 ed 06 00 00    	jne    0x720
  33:	49 3b ad b8 04 00 00 	cmp    0x4b8(%r13),%rbp
  3a:	0f                   	.byte 0xf
  3b:	84 77 05             	test   %dh,0x5(%rdi)


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