[syzbot] [dri?] WARNING in vkms_get_vblank_timestamp

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4b0f4525dc4f Add linux-next specific files for 20230331
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13ea0159c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=85cc4b935a1f7194
dashboard link: https://syzkaller.appspot.com/bug?extid=75cc0f9f7e6324dd2501
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=15cb3659c80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8d06bb015df3/disk-4b0f4525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6a1c1ebf3724/vmlinux-4b0f4525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4bb2b8d6cd7d/bzImage-4b0f4525.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+75cc0f...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 6019 at drivers/gpu/drm/vkms/vkms_crtc.c:103 vkms_get_vblank_timestamp+0x1cf/0x240 drivers/gpu/drm/vkms/vkms_crtc.c:103
Modules linked in:
CPU: 1 PID: 6019 Comm: syz-executor.1 Not tainted 6.3.0-rc4-next-20230331-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:vkms_get_vblank_timestamp+0x1cf/0x240 drivers/gpu/drm/vkms/vkms_crtc.c:103
Code: ce 73 fc e8 53 e9 63 fc 4c 89 e1 48 ba 00 00 00 00 00 fc ff df 48 c1 e9 03 80 3c 11 00 75 65 49 89 04 24 eb c4 e8 b1 ce 73 fc <0f> 0b eb bb e8 d8 80 c6 fc e9 de fe ff ff e8 0e 81 c6 fc e9 78 fe
RSP: 0018:ffffc9000b3873d8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000004e19fc6e8a RCX: 0000000000000000
RDX: ffff8880756257c0 RSI: ffffffff850f429f RDI: 0000000000000006
RBP: ffff88801dc84000 R08: 0000000000000006 R09: 0000004e19fc6e8a
R10: 0000004e19fc6e8a R11: 0000000000000000 R12: ffffc9000b387540
R13: 0000004e19fc6e8a R14: 0000000000004e20 R15: ffffffff850f40d0
FS: 00007f5372809700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000202fc000 CR3: 0000000027361000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
drm_crtc_get_last_vbltimestamp+0x102/0x1a0 drivers/gpu/drm/drm_vblank.c:877
drm_crtc_next_vblank_start+0x13f/0x2b0 drivers/gpu/drm/drm_vblank.c:1006
set_fence_deadline drivers/gpu/drm/drm_atomic_helper.c:1531 [inline]
drm_atomic_helper_wait_for_fences+0x1b4/0x780 drivers/gpu/drm/drm_atomic_helper.c:1578
drm_atomic_helper_commit drivers/gpu/drm/drm_atomic_helper.c:2007 [inline]
drm_atomic_helper_commit+0x1bd/0x370 drivers/gpu/drm/drm_atomic_helper.c:1979
drm_atomic_commit+0x20a/0x300 drivers/gpu/drm/drm_atomic.c:1503
drm_client_modeset_commit_atomic+0x69b/0x7e0 drivers/gpu/drm/drm_client_modeset.c:1045
drm_client_modeset_commit_locked+0x149/0x580 drivers/gpu/drm/drm_client_modeset.c:1148
pan_display_atomic drivers/gpu/drm/drm_fb_helper.c:1690 [inline]
drm_fb_helper_pan_display+0x28f/0x970 drivers/gpu/drm/drm_fb_helper.c:1750
fb_pan_display+0x2fb/0x6c0 drivers/video/fbdev/core/fbmem.c:924
bit_update_start+0x49/0x1f0 drivers/video/fbdev/core/bitblit.c:387
fbcon_switch+0xbcf/0x1380 drivers/video/fbdev/core/fbcon.c:2169
redraw_screen+0x2bd/0x740 drivers/tty/vt/vt.c:965
fbcon_modechanged+0x526/0x620 drivers/video/fbdev/core/fbcon.c:2704
fbcon_update_vcs+0x3e/0x50 drivers/video/fbdev/core/fbcon.c:2749
do_fb_ioctl+0x6d7/0x740 drivers/video/fbdev/core/fbmem.c:1125
fb_ioctl+0xeb/0x150 drivers/video/fbdev/core/fbmem.c:1202
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f5371a8c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5372809168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f5371bac050 RCX: 00007f5371a8c0f9
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000005
RBP: 00007f5371ae7b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd0e5e571f R14: 00007f5372809300 R15: 0000000000022000
</TASK>


---
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[Daniel Vetter]

On Thu, Apr 06, 2023 at 10:57:48AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 4b0f4525dc4f Add linux-next specific files for 20230331
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13ea0159c80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=85cc4b935a1f7194
> dashboard link: https://syzkaller.appspot.com/bug?extid=75cc0f9f7e6324dd2501
> 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=15cb3659c80000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/8d06bb015df3/disk-4b0f4525.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6a1c1ebf3724/vmlinux-4b0f4525.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4bb2b8d6cd7d/bzImage-4b0f4525.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+75cc0f...@syzkaller.appspotmail.com

Should be fixed with f2c7ca890182 ("drm/atomic-helper: Don't set deadline
for modesets"). And maybe also 6f1ccbf07453 ("drm/vblank: Fix for drivers
that do not drm_vblank_init()").

Would be great if you can confirm. The regression was introduced in
d39e48ca80c0 ("drm/atomic-helper: Set fence deadline for vblank") if my
guess is correct.
-Daniel

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

[Aleksandr Nogikh]

On Thu, Apr 6, 2023 at 8:59 PM Daniel Vetter <dan...@ffwll.ch> wrote:
>
> On Thu, Apr 06, 2023 at 10:57:48AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 4b0f4525dc4f Add linux-next specific files for 20230331
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13ea0159c80000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=85cc4b935a1f7194
> > dashboard link: https://syzkaller.appspot.com/bug?extid=75cc0f9f7e6324dd2501
> > 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=15cb3659c80000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/8d06bb015df3/disk-4b0f4525.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/6a1c1ebf3724/vmlinux-4b0f4525.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/4bb2b8d6cd7d/bzImage-4b0f4525.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+75cc0f...@syzkaller.appspotmail.com
>
> Should be fixed with f2c7ca890182 ("drm/atomic-helper: Don't set deadline
> for modesets"). And maybe also 6f1ccbf07453 ("drm/vblank: Fix for drivers
> that do not drm_vblank_init()").
>
> Would be great if you can confirm. The regression was introduced in
> d39e48ca80c0 ("drm/atomic-helper: Set fence deadline for vblank") if my
> guess is correct.
> -Daniel

Let's ask the bot to retest the reproducer

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
master

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[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+75cc0f...@syzkaller.appspotmail.com

Tested on:

commit: 7d8214bb Add linux-next specific files for 20230412
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1387763dc80000
kernel config: https://syzkaller.appspot.com/x/.config?x=923e20c1867d7c1c

dashboard link: https://syzkaller.appspot.com/bug?extid=75cc0f9f7e6324dd2501
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[Aleksandr Nogikh]

Let's close the bug on syzbot so that the bot can report similar bugs
in the future:

#syz fix: drm/atomic-helper: Don't set deadline for modesets