[syzbot] general protection fault in vhost_iotlb_itree_first

[syzbot <syzbot+bbb030fc51d6f3c5d067@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    359303076163 tty: n_tty: do not look ahead for EOL charact..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b34b54700000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da674567f7b6043d
dashboard link: https://syzkaller.appspot.com/bug?extid=bbb030fc51d6f3c5d067
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+bbb030fc51d6f3c5d067@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 17981 Comm: vhost-17980 Not tainted 5.17.0-rc4-syzkaller-00052-g359303076163 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:vhost_iotlb_itree_iter_first drivers/vhost/iotlb.c:19 [inline]
RIP: 0010:vhost_iotlb_itree_first+0x29/0x280 drivers/vhost/iotlb.c:169
Code: 00 41 57 41 56 41 55 49 89 d5 41 54 55 48 89 fd 53 48 89 f3 e8 e8 eb a0 fa 48 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 e8 01 00 00 4c 8b 65 00 4d 85 e4 0f 84 b3 01 00
RSP: 0018:ffffc90004f57ac8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 30303030320a0028 RCX: ffffc900103dc000
RDX: 0000000000000000 RSI: ffffffff86d72738 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000002
R10: ffffffff86d62d88 R11: 0000000000000000 R12: ffff8880260e4d68
R13: 303030305f3a3057 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2d46121901 CR3: 000000001d652000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 translate_desc+0x11e/0x3e0 drivers/vhost/vhost.c:2054
 vhost_get_vq_desc+0x662/0x22c0 drivers/vhost/vhost.c:2300
 vhost_vsock_handle_tx_kick+0x277/0xa20 drivers/vhost/vsock.c:522
 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
 kthread+0x2e9/0x3a0 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vhost_iotlb_itree_iter_first drivers/vhost/iotlb.c:19 [inline]
RIP: 0010:vhost_iotlb_itree_first+0x29/0x280 drivers/vhost/iotlb.c:169
Code: 00 41 57 41 56 41 55 49 89 d5 41 54 55 48 89 fd 53 48 89 f3 e8 e8 eb a0 fa 48 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 e8 01 00 00 4c 8b 65 00 4d 85 e4 0f 84 b3 01 00
RSP: 0018:ffffc90004f57ac8 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 30303030320a0028 RCX: ffffc900103dc000
RDX: 0000000000000000 RSI: ffffffff86d72738 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000002
R10: ffffffff86d62d88 R11: 0000000000000000 R12: ffff8880260e4d68
R13: 303030305f3a3057 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2d449f6718 CR3: 000000001d652000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	00 41 57             	add    %al,0x57(%rcx)
   3:	41 56                	push   %r14
   5:	41 55                	push   %r13
   7:	49 89 d5             	mov    %rdx,%r13
   a:	41 54                	push   %r12
   c:	55                   	push   %rbp
   d:	48 89 fd             	mov    %rdi,%rbp
  10:	53                   	push   %rbx
  11:	48 89 f3             	mov    %rsi,%rbx
  14:	e8 e8 eb a0 fa       	callq  0xfaa0ec01
  19:	48 89 ea             	mov    %rbp,%rdx
  1c:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  23:	fc ff df
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 e8 01 00 00    	jne    0x21c
  34:	4c 8b 65 00          	mov    0x0(%rbp),%r12
  38:	4d 85 e4             	test   %r12,%r12
  3b:	0f                   	.byte 0xf
  3c:	84                   	.byte 0x84
  3d:	b3 01                	mov    $0x1,%bl


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