Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756645Ab3ILUEJ (ORCPT ); Thu, 12 Sep 2013 16:04:09 -0400 Received: from mail-ie0-f170.google.com ([209.85.223.170]:54855 "EHLO mail-ie0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755450Ab3ILUEG (ORCPT ); Thu, 12 Sep 2013 16:04:06 -0400 MIME-Version: 1.0 X-Originating-IP: [178.83.130.250] In-Reply-To: References: <20130912150645.GZ31370@twins.programming.kicks-ass.net> <20130912154329.GB31370@twins.programming.kicks-ass.net> <20130912162210.GE31370@twins.programming.kicks-ass.net> Date: Thu, 12 Sep 2013 22:04:03 +0200 Message-ID: Subject: Re: [BUG] completely bonkers use of set_need_resched + VM_FAULT_NOPAGE From: Daniel Vetter To: Thomas Gleixner Cc: Peter Zijlstra , Dave Airlie , Maarten Lankhorst , Thomas Hellstrom , intel-gfx , dri-devel , Linux Kernel Mailing List , Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1399 Lines: 31 On Thu, Sep 12, 2013 at 9:58 PM, Thomas Gleixner wrote: > >> On Thu, Sep 12, 2013 at 6:22 PM, Peter Zijlstra wrote: >> > If 'sane' userspace is never supposed to do this, then only insane >> > userspace is going to hurt from this and that's a GOOD (tm) thing, >> > right? ;-) >> >> Afaik sane userspace doesn't hit the _deadlock_ (or lifelock if we >> have the set_need_resched in there). drm/i915 is a bit different since >> we have just one lock, and so the same design would actually deadlock >> even for sane userspace. But hitting contention there and yielding is >> somewhat expected. Obviously shouldn't happen too often since it'll >> hurt performance, with either blocking or the yield spinning loop. > > So this is actually a non priviledged DoS interface, right? 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 ... -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/