Re: WARNING in md_ioctl

[Daniel Vetter]

On Mon, Nov 25, 2019 at 02:37:01PM -0800, syzbot wrote:
> syzbot has bisected this bug to:
> 
> commit 4b6ce6810a5dc0af387a238e8c852e0d3822381f
> Author: Rafael Antognolli <rafael.antognolli@xxxxxxxxx>
> Date:   Mon Feb 5 23:33:30 2018 +0000
> 
>     drm/i915/cnl: WaPipeControlBefore3DStateSamplePattern

This seems very unlikely, the reproducer doesn't open a drm device, and
I'd be surprised if your gcd instances have an actual i915 device in them
(but I can't check because boot log isn't provided, didn't find it on the
dashboard either).

Since i915 is built-in I suspect this simply moved something else in the
kernel image around which provokes the bug.
-Daniel

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13aeb522e00000
> start commit:   c61a56ab Merge branch 'x86-urgent-for-linus' of git://git...
> git tree:       upstream
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=106eb522e00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17aeb522e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4013180e7c7a9ff9
> dashboard link: https://syzkaller.appspot.com/bug?extid=1e46a0864c1a6e9bd3d8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16bca207800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14819a47800000
> 
> Reported-by: syzbot+1e46a0864c1a6e9bd3d8@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 4b6ce6810a5d ("drm/i915/cnl:
> WaPipeControlBefore3DStateSamplePattern")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch