[syzbot] general protection fault in virtio_gpu_poll

[syzbot <syzbot+4af2eec0d32a135ba67e@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    fe91c4725aee Merge tag 'scsi-misc' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=173a8aeab00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7d0e8aeec50207a6
dashboard link: https://syzkaller.appspot.com/bug?extid=4af2eec0d32a135ba67e
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+4af2eec0d32a135ba67e@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 PID: 27453 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:virtio_gpu_poll+0x7c/0x440 drivers/gpu/drm/virtio/virtgpu_drv.c:169
Code: 48 c1 ea 03 80 3c 02 00 0f 85 2b 03 00 00 4c 8b ab b0 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7d 18 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 03 00 00 4d 8b 6d 18 31 ff 4c 89 ee e8 8c 50
RSP: 0018:ffffc90024f0f708 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888078deb000 RCX: ffffc9002783b000
RDX: 0000000000000003 RSI: ffffffff8462b2d5 RDI: 0000000000000018
RBP: ffff88801f33ba80 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff81cd631d R11: 0000000000000000 R12: ffffc90024f0f898
R13: 0000000000000000 R14: 0000000000000010 R15: 0000000000000004
FS:  00007f5ce5906700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5ce84009e8 CR3: 000000006c1f7000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8cb/0x16a0 fs/select.c:534
 core_sys_select+0x3c2/0x9c0 fs/select.c:677
 do_pselect.constprop.0+0x17b/0x1c0 fs/select.c:759
 __do_sys_pselect6 fs/select.c:800 [inline]
 __se_sys_pselect6 fs/select.c:791 [inline]
 __x64_sys_pselect6+0x1c5/0x2b0 fs/select.c:791
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f5ce8390ae9
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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5ce5906188 EFLAGS: 00000246 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 00007f5ce84a3f60 RCX: 00007f5ce8390ae9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000040
RBP: 00007f5ce83eaf25 R08: 0000000020000380 R09: 0000000000000000
R10: 0000000020000140 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd10da36cf R14: 00007f5ce5906300 R15: 0000000000022000
 </TASK>
Modules linked in:
---[ end trace 1158ebbbb6efaa79 ]---
RIP: 0010:virtio_gpu_poll+0x7c/0x440 drivers/gpu/drm/virtio/virtgpu_drv.c:169
Code: 48 c1 ea 03 80 3c 02 00 0f 85 2b 03 00 00 4c 8b ab b0 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7d 18 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 19 03 00 00 4d 8b 6d 18 31 ff 4c 89 ee e8 8c 50
RSP: 0018:ffffc90024f0f708 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff888078deb000 RCX: ffffc9002783b000
RDX: 0000000000000003 RSI: ffffffff8462b2d5 RDI: 0000000000000018
RBP: ffff88801f33ba80 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff81cd631d R11: 0000000000000000 R12: ffffc90024f0f898
R13: 0000000000000000 R14: 0000000000000010 R15: 0000000000000004
FS:  00007f5ce5906700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5ce84009e8 CR3: 000000006c1f7000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
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 2b 03 00 00    	jne    0x339
   e:	4c 8b ab b0 01 00 00 	mov    0x1b0(%rbx),%r13
  15:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  1c:	fc ff df
  1f:	49 8d 7d 18          	lea    0x18(%r13),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 19 03 00 00    	jne    0x34d
  34:	4d 8b 6d 18          	mov    0x18(%r13),%r13
  38:	31 ff                	xor    %edi,%edi
  3a:	4c 89 ee             	mov    %r13,%rsi
  3d:	e8                   	.byte 0xe8
  3e:	8c                   	.byte 0x8c
  3f:	50                   	push   %rax


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