Re: [syzbot] WARNING in drm_wait_one_vblank

[syzbot <syzbot+6f7fe2dbc479dca0ed17@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    6f513529296f Merge tag 'for-5.16-rc4-tag' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16499fc5b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=221ffc09e39ebbd1
dashboard link: https://syzkaller.appspot.com/bug?extid=6f7fe2dbc479dca0ed17
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17ab646db00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17767fc5b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6f7fe2dbc479dca0ed17@syzkaller.appspotmail.com

platform vkms: vblank wait timed out on crtc 0
WARNING: CPU: 1 PID: 3708 at drivers/gpu/drm/drm_vblank.c:1269 drm_wait_one_vblank+0x2bc/0x500 drivers/gpu/drm/drm_vblank.c:1269
Modules linked in:

CPU: 1 PID: 3708 Comm: syz-executor955 Not tainted 5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:drm_wait_one_vblank+0x2bc/0x500 drivers/gpu/drm/drm_vblank.c:1269
Code: 85 f6 0f 84 a3 01 00 00 e8 11 4c 1a fd 4c 89 ef e8 f9 34 13 00 44 89 e1 4c 89 f2 48 c7 c7 40 7d 1a 8a 48 89 c6 e8 7f 61 a3 04 <0f> 0b e9 87 fe ff ff e8 e8 4b 1a fd 31 ff 4c 89 ee e8 6e 4e 1a fd
RSP: 0018:ffffc9000298fb40 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000596 RCX: 0000000000000000
RDX: ffff8880766f3a00 RSI: ffffffff815f1e08 RDI: fffff52000531f5a
RBP: ffff8881469f4000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815ebbae R11: 0000000000000000 R12: 0000000000000000
R13: ffff888146e02010 R14: ffff888146cc7500 R15: ffff888146e10030
FS:  00005555572d9300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa33cdb0290 CR3: 0000000079034000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 drm_fb_helper_ioctl+0x159/0x1a0 drivers/gpu/drm/drm_fb_helper.c:1197
 do_fb_ioctl+0x1d5/0x690 drivers/video/fbdev/core/fbmem.c:1175
 fb_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1189
 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: 0033:0x7fa33cd3c1c9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc7e8b9d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000000f4240 RCX: 00007fa33cd3c1c9
RDX: 0000000000000000 RSI: 0000000040044620 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000016e91
R13: 00007ffc7e8b9dac R14: 00007ffc7e8b9dd0 R15: 00007ffc7e8b9dc0
 </TASK>