Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751488Ab3COEub (ORCPT ); Fri, 15 Mar 2013 00:50:31 -0400 Received: from 209-20-75-48.static.cloud-ips.com ([209.20.75.48]:43470 "EHLO shiva.localdomain" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750861Ab3COEua (ORCPT ); Fri, 15 Mar 2013 00:50:30 -0400 Date: Thu, 14 Mar 2013 21:43:29 -0700 From: Ben Widawsky To: Chris Wilson Cc: Tommi Rantala , David Airlie , Daniel Vetter , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Dave Jones Subject: Re: [Intel-gfx] [PATCH] drm/i915: Sanity check incoming ioctl data for a NULL pointer Message-ID: <20130315044328.GA14210@bwidawsk.net> References: <1363265997-29023-1-git-send-email-chris@chris-wilson.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1363265997-29023-1-git-send-email-chris@chris-wilson.co.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2554 Lines: 72 On Thu, Mar 14, 2013 at 12:59:57PM +0000, Chris Wilson wrote: > In order to prevent a potential NULL deference with hostile userspace, > we need to check whether the ioctl was passed an invalid args pointer. > > Reported-by: Tommi Rantala > Link: http://lkml.kernel.org/r/CA+ydwtpuBvbwxbt-tdgPUvj1EU7itmCHo_2B3w13HkD5+jWKow@mail.gmail.com > Signed-off-by: Chris Wilson > --- > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > index 365e41a..9f5602e 100644 > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > @@ -1103,7 +1103,11 @@ i915_gem_execbuffer(struct drm_device *dev, void *data, > struct drm_i915_gem_exec_object2 *exec2_list = NULL; > int ret, i; > > - if (args->buffer_count < 1) { > + if (args == NULL) > + return -EINVAL; > + > + if (args->buffer_count < 1 || > + args->buffer_count > INT_MAX / sizeof(*exec2_list)) { > DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count); > return -EINVAL; > } > @@ -1182,8 +1186,11 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data, > struct drm_i915_gem_exec_object2 *exec2_list = NULL; > int ret; > > + if (args == NULL) > + return -EINVAL; > + > if (args->buffer_count < 1 || > - args->buffer_count > UINT_MAX / sizeof(*exec2_list)) { > + args->buffer_count > INT_MAX / sizeof(*exec2_list)) { > DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count); > return -EINVAL; > } Why did you change UINT_MAX to INT_MAX? TBH, I'm confused what we're trying to achieve, and why we need anything other than: if (!args->buffer_count) I'm also not seeing how the NULL checks are needed since at least it seems to be for execbuffer (IOW) we could never have NULL args. if (cmd & (IOC_IN | IOC_OUT)) { if (asize <= sizeof(stack_kdata)) { kdata = stack_kdata; } else { kdata = kmalloc(asize, GFP_KERNEL); if (!kdata) { retcode = -ENOMEM; goto err_i1; } } if (asize > usize) memset(kdata + usize, 0, asize - usize); } Sorry if these are stupid questions. -- Ben Widawsky, Intel Open Source Technology Center -- 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/