linux-kernel - Re: [BUG] completely bonkers use of set_need_resched + VM_FAULT

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Message-ID: <CAKMK7uHqufs64=pD=o--958Ns+NAsrwUTNpcd2_WGQnoJRnfOQ@mail.gmail.com>
Date:	Thu, 12 Sep 2013 22:23:02 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Dave Airlie <airlied@...ux.ie>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Thomas Hellstrom <thellstrom@...are.com>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [BUG] completely bonkers use of set_need_resched + VM_FAULT_NOPAGE

On Thu, Sep 12, 2013 at 10:20 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>> I think for ttm drivers it's just execbuf being exploitable. But on
>> drm/i915 we've
>> had the same issue with the pwrite/pread ioctls, so a simple
>> glBufferData(glMap) kind of recursion from gl clients blew the kernel
>> to pieces ...
>
> And the only answer you folks came up with is set_need_resched() and
> yield()? Oh well....

The yield was for a different lifelock, and that one is also fixed by
now. The fault handler deadlock was fixed in the usual "drop locks and
jump into slowpath" fasion, at least in drm/i915.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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