[syzbot] general protection fault in virtio_gpu_object_create

[syzbot <syzbot+62d1cf88cc39247b2e23@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    136057256686 Linux 5.16-rc2
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14029126b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf85c53718a1e697
dashboard link: https://syzkaller.appspot.com/bug?extid=62d1cf88cc39247b2e23
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+62d1cf88cc39247b2e23@syzkaller.appspotmail.com

RBP: 00007f96f6d2a1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffde5383b0f R14: 00007f96f6d2a300 R15: 0000000000022000
 </TASK>
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 3 PID: 32308 Comm: syz-executor.2 Not tainted 5.16.0-rc2-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:virtio_gpu_object_shmem_init drivers/gpu/drm/virtio/virtgpu_object.c:183 [inline]
RIP: 0010:virtio_gpu_object_create+0x29b/0xd90 drivers/gpu/drm/virtio/virtgpu_object.c:249
Code: 89 de e8 38 11 09 fd 48 85 db 0f 85 9f 03 00 00 e8 9a 0e 09 fd 49 8d 7f 0c 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 82
RSP: 0018:ffffc90002fafad0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc900242c8000
RDX: 0000000000000000 RSI: ffffffff846dc446 RDI: 0000000000000000
RBP: ffff8880257af000 R08: 0000000000000000 R09: ffffffff8bcca173
R10: ffffffff846dc438 R11: 0000000000000000 R12: ffffc90002fafbd0
R13: ffff8880430e0010 R14: ffff8880430e0000 R15: fffffffffffffff4
FS:  00007f96f6d2a700(0000) GS:ffff88802cd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000009af988 CR3: 0000000053153000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 virtio_gpu_gem_create drivers/gpu/drm/virtio/virtgpu_gem.c:42 [inline]
 virtio_gpu_mode_dumb_create+0x319/0x5c0 drivers/gpu/drm/virtio/virtgpu_gem.c:90
 drm_mode_create_dumb+0x26c/0x2f0 drivers/gpu/drm/drm_dumb_buffers.c:96
 drm_ioctl_kernel+0x27d/0x4e0 drivers/gpu/drm/drm_ioctl.c:782
 drm_ioctl+0x51e/0x9d0 drivers/gpu/drm/drm_ioctl.c:885
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
 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: 0033:0x7f96f97b4ae9
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:00007f96f6d2a188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f96f98c7f60 RCX: 00007f96f97b4ae9
RDX: 0000000020000040 RSI: 00000000c02064b2 RDI: 0000000000000003
RBP: 00007f96f6d2a1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffde5383b0f R14: 00007f96f6d2a300 R15: 0000000000022000
 </TASK>
Modules linked in:
---[ end trace 7991b533e1b66750 ]---
RIP: 0010:virtio_gpu_object_shmem_init drivers/gpu/drm/virtio/virtgpu_object.c:183 [inline]
RIP: 0010:virtio_gpu_object_create+0x29b/0xd90 drivers/gpu/drm/virtio/virtgpu_object.c:249
Code: 89 de e8 38 11 09 fd 48 85 db 0f 85 9f 03 00 00 e8 9a 0e 09 fd 49 8d 7f 0c 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 82
RSP: 0018:ffffc90002fafad0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc900242c8000
RDX: 0000000000000000 RSI: ffffffff846dc446 RDI: 0000000000000000
RBP: ffff8880257af000 R08: 0000000000000000 R09: ffffffff8bcca173
R10: ffffffff846dc438 R11: 0000000000000000 R12: ffffc90002fafbd0
R13: ffff8880430e0010 R14: ffff8880430e0000 R15: fffffffffffffff4
FS:  00007f96f6d2a700(0000) GS:ffff88802cd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000009af988 CR3: 0000000053153000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	89 de                	mov    %ebx,%esi
   2:	e8 38 11 09 fd       	callq  0xfd09113f
   7:	48 85 db             	test   %rbx,%rbx
   a:	0f 85 9f 03 00 00    	jne    0x3af
  10:	e8 9a 0e 09 fd       	callq  0xfd090eaf
  15:	49 8d 7f 0c          	lea    0xc(%r15),%rdi
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
  2e:	48 89 f8             	mov    %rdi,%rax
  31:	83 e0 07             	and    $0x7,%eax
  34:	83 c0 03             	add    $0x3,%eax
  37:	38 d0                	cmp    %dl,%al
  39:	7c 08                	jl     0x43
  3b:	84 d2                	test   %dl,%dl
  3d:	0f                   	.byte 0xf
  3e:	85                   	.byte 0x85
  3f:	82                   	.byte 0x82


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