Re: INFO: task hung in fb_open

Re: INFO: task hung in fb_open

[syzbot]

syzbot has bisected this bug to:

commit 979c11ef39cee79d6f556091a357890962be2580
Author: Ayan Kumar Halder <ayan.halder@arm.com>
Date:   Tue Jul 17 17:13:46 2018 +0000

     drm/sun4i: Substitute sun4i_backend_format_is_yuv() with format->is_yuv

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15d2f97ee00000
start commit:   596cf45c Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13d2f97ee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7d8ab2e0e09c2a82
dashboard link: https://syzkaller.appspot.com/bug?extid=a4ae1442ccc637162dc1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14273edae00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e7677ae00000

Reported-by: syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com
Fixes: 979c11ef39ce ("drm/sun4i: Substitute sun4i_backend_format_is_yuv()  
with format->is_yuv")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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Re: INFO: task hung in fb_open

[Daniel Vetter]

On Thu, Dec 5, 2019 at 2:38 PM syzbot
<syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com> wrote:
>
> syzbot has bisected this bug to:
>
> commit 979c11ef39cee79d6f556091a357890962be2580
> Author: Ayan Kumar Halder <ayan.halder@arm.com>
> Date:   Tue Jul 17 17:13:46 2018 +0000
>
>      drm/sun4i: Substitute sun4i_backend_format_is_yuv() with format->is_yuv

Pretty sure your GCD machine is not using the sun4i driver. It's also
very far away from the code that's blowing up. bisect gone wrong?
-Daniel

>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15d2f97ee00000
> start commit:   596cf45c Merge branch 'akpm' (patches from Andrew)
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13d2f97ee00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7d8ab2e0e09c2a82
> dashboard link: https://syzkaller.appspot.com/bug?extid=a4ae1442ccc637162dc1
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14273edae00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e7677ae00000
>
> Reported-by: syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com
> Fixes: 979c11ef39ce ("drm/sun4i: Substitute sun4i_backend_format_is_yuv()
> with format->is_yuv")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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Re: INFO: task hung in fb_open

[Dmitry Vyukov]

On Thu, Dec 5, 2019 at 3:05 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Thu, Dec 5, 2019 at 2:38 PM syzbot
> <syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com> wrote:
> >
> > syzbot has bisected this bug to:
> >
> > commit 979c11ef39cee79d6f556091a357890962be2580
> > Author: Ayan Kumar Halder <ayan.halder@arm.com>
> > Date:   Tue Jul 17 17:13:46 2018 +0000
> >
> >      drm/sun4i: Substitute sun4i_backend_format_is_yuv() with format->is_yuv
>
> Pretty sure your GCD machine is not using the sun4i driver. It's also
> very far away from the code that's blowing up. bisect gone wrong?
> -Daniel

Yes, this driver is not even enabled in the config.
I see 2 issues with kernel in the bisect log:
1. Unrelated machine hangs get in the way of bisection process (or
that "no output" another manifestation of this bug?).
2. Somehow this change to not compiled file changed vmlinux thus
detection of unrelated changes failed. Non-deterministic kernel builds
issue is tracked here:
https://github.com/google/syzkaller/issues/1271#issuecomment-559093018
but so far I don't have any glues/ideas.


> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15d2f97ee00000
> > start commit:   596cf45c Merge branch 'akpm' (patches from Andrew)
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13d2f97ee00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=7d8ab2e0e09c2a82
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a4ae1442ccc637162dc1
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14273edae00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e7677ae00000
> >
> > Reported-by: syzbot+a4ae1442ccc637162dc1@syzkaller.appspotmail.com
> > Fixes: 979c11ef39ce ("drm/sun4i: Substitute sun4i_backend_format_is_yuv()
> > with format->is_yuv")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
> --
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