From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474Ab2LJH2Z (ORCPT ); Mon, 10 Dec 2012 02:28:25 -0500 Received: from mga11.intel.com ([192.55.52.93]:48668 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185Ab2LJH2X (ORCPT ); Mon, 10 Dec 2012 02:28:23 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,250,1355126400"; d="scan'208";a="261729927" From: Jani Nikula To: Tim Gardner , linux-kernel@vger.kernel.org Cc: Tim Gardner , Daniel Vetter , David Airlie , dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2 linux-next] i915: intel_set_mode: Reduce stack allocation from 500 bytes to 2 pointers In-Reply-To: <1354892066-30256-1-git-send-email-tim.gardner@canonical.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <87zk1qm6cd.fsf@intel.com> <1354892066-30256-1-git-send-email-tim.gardner@canonical.com> User-Agent: Notmuch/0.14+142~gf454854 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Date: Mon, 10 Dec 2012 09:29:17 +0200 Message-ID: <87obi2mkky.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 07 Dec 2012, Tim Gardner wrote: > smatch warning: > > drivers/gpu/drm/i915/intel_display.c:7019 intel_set_mode() warn: function puts > 500 bytes on stack > > Refactor so that saved_mode and saved_hwmode are dynamically allocated as opposed > to being automatic variables. 500 bytes seems like it could run the potential for blowing > the kernel stack. Reviewed-by: Jani Nikula > > Cc: Daniel Vetter > Cc: David Airlie > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: Tim Gardner > --- > > V2 - spaces around '*', use kmalloc instead of kzalloc(). Missed > error return that would have orphaned memory. > > drivers/gpu/drm/i915/intel_display.c | 22 ++++++++++++++++------ > 1 file changed, 16 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > index de51489..c15b21b 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -7739,11 +7739,18 @@ bool intel_set_mode(struct drm_crtc *crtc, > { > struct drm_device *dev = crtc->dev; > drm_i915_private_t *dev_priv = dev->dev_private; > - struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode; > + struct drm_display_mode *adjusted_mode, *saved_mode, *saved_hwmode; > struct intel_crtc *intel_crtc; > unsigned disable_pipes, prepare_pipes, modeset_pipes; > bool ret = true; > > + saved_mode = kmalloc(2 * sizeof(*saved_mode), GFP_KERNEL); > + if (!saved_mode) { > + DRM_ERROR("i915: Could not allocate saved display mode.\n"); > + return false; > + } > + saved_hwmode = saved_mode + 1; > + > intel_modeset_affected_pipes(crtc, &modeset_pipes, > &prepare_pipes, &disable_pipes); > > @@ -7753,8 +7760,8 @@ bool intel_set_mode(struct drm_crtc *crtc, > for_each_intel_crtc_masked(dev, disable_pipes, intel_crtc) > intel_crtc_disable(&intel_crtc->base); > > - saved_hwmode = crtc->hwmode; > - saved_mode = crtc->mode; > + *saved_hwmode = crtc->hwmode; > + *saved_mode = crtc->mode; > > /* Hack: Because we don't (yet) support global modeset on multiple > * crtcs, we don't keep track of the new mode for more than one crtc. > @@ -7765,7 +7772,8 @@ bool intel_set_mode(struct drm_crtc *crtc, > if (modeset_pipes) { > adjusted_mode = intel_modeset_adjusted_mode(crtc, mode); > if (IS_ERR(adjusted_mode)) { > - return false; > + ret = false; > + goto out; > } > } > > @@ -7817,12 +7825,14 @@ bool intel_set_mode(struct drm_crtc *crtc, > done: > drm_mode_destroy(dev, adjusted_mode); > if (!ret && crtc->enabled) { > - crtc->hwmode = saved_hwmode; > - crtc->mode = saved_mode; > + crtc->hwmode = *saved_hwmode; > + crtc->mode = *saved_mode; > } else { > intel_modeset_check_state(dev); > } > > +out: > + kfree(saved_mode); > return ret; > } > > -- > 1.7.9.5