linux-kernel - Re: WARN_ON() and X session lost from i915 on 3.14-rc6

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Message-ID: <20140313090549.GA8998@nuc-i3427.alporthouse.com>
Date:	Thu, 13 Mar 2014 09:05:49 +0000
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Pavel Machek <pavel@....cz>
Cc:	daniel.vetter@...ll.ch, jani.nikula@...ux.intel.com,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: WARN_ON() and X session lost from i915 on 3.14-rc6

On Thu, Mar 13, 2014 at 09:40:02AM +0100, Pavel Machek wrote:
> On Wed 2014-03-12 23:52:09, Chris Wilson wrote:
> > On Thu, Mar 13, 2014 at 12:30:39AM +0100, Pavel Machek wrote:
> > > Hi!
> > > 
> > > This cost me two half-written mails...
> > > 
> > > So far it happened once, so it may be very infrequent; but I do not
> > > think I seen similar failure from i915 before, so it may be an
> > > regression. Well...
> > 
> > It's a userspace use-after-free bug. Please file a bug on
> > bugs.freedesktop.org.
> 
> Could we get some better messages from the kernel? Userspace should
> not be able to produce WARN_ON()s.

Indeed, we have already pruned those errors and WARNs, in favour of a
real error code, precisely because they are user triggerable.
 
> (This is debian 6.0.8; do you think it is worth reporting? I don't
> think I should go to bugs.freedesktop.org...)

I guess your userspace is roughly xf86-video-intel-2.17 and friends.
Quite a few changes since then, but I've forgotten if this bug was ever
addressed explicitly. Most likely it has been...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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