From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:36674 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752827AbcEDRLi (ORCPT ); Wed, 4 May 2016 13:11:38 -0400 Received: by mail-wm0-f67.google.com with SMTP id w143so11775461wmw.3 for ; Wed, 04 May 2016 10:11:37 -0700 (PDT) Date: Wed, 4 May 2016 19:11:35 +0200 From: Daniel Vetter To: Lyude Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, open list , stable@vger.kernel.org Subject: Re: [PATCH 2/3] drm/fb_helper: Fix references to dev->mode_config.num_connector Message-ID: <20160504171135.GF1286@phenom.ffwll.local> References: <1462375734-8213-1-git-send-email-cpaul@redhat.com> <1462375734-8213-2-git-send-email-cpaul@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1462375734-8213-2-git-send-email-cpaul@redhat.com> Sender: stable-owner@vger.kernel.org List-ID: On Wed, May 04, 2016 at 11:28:52AM -0400, Lyude wrote: > During boot, MST hotplugs are generally expected (even if no physical > hotplugging occurs) and result in DRM's connector topology changing. > This means that using num_connector from the current mode configuration > can lead to the number of connectors changing under us. This can lead to > some nasty scenarios in fbcon: > > - We allocate an array to the size of dev->mode_config.num_connectors. > - MST hotplug occurs, dev->mode_config.num_connectors gets incremented. > - We try to loop through each element in the array using the new value > of dev->mode_config.num_connectors, and end up going out of bounds > since dev->mode_config.num_connectors is now larger then the array we > allocated. > > fb_helper->connector_count however, will always remain consistent while > we do a modeset in fb_helper. > > Cc: stable@vger.kernel.org > Signed-off-by: Lyude Ok, this one looks like it's indeed in the same critical section (within drm_setup_outputs) as where we allocate the fb helper connector array. So I think this one here is not needed to fix a bug? Still makes sense as a patch, but not with cc: stable I think. -Daniel > --- > drivers/gpu/drm/drm_fb_helper.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > index 855108e..15204c0 100644 > --- a/drivers/gpu/drm/drm_fb_helper.c > +++ b/drivers/gpu/drm/drm_fb_helper.c > @@ -1914,7 +1914,7 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper, > if (modes[n] == NULL) > return best_score; > > - crtcs = kzalloc(dev->mode_config.num_connector * > + crtcs = kzalloc(fb_helper->connector_count * > sizeof(struct drm_fb_helper_crtc *), GFP_KERNEL); > if (!crtcs) > return best_score; > @@ -1960,7 +1960,7 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper, > if (score > best_score) { > best_score = score; > memcpy(best_crtcs, crtcs, > - dev->mode_config.num_connector * > + fb_helper->connector_count * > sizeof(struct drm_fb_helper_crtc *)); > } > } > -- > 2.5.5 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch