| Message ID | 1462375734-8213-2-git-send-email-cpaul@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <cpaul@redhat.com> 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
I would Cc it to stable just in case tbh. I picked up on this one since KASAN was picking up on some of the memcpy() calls around here going out of bounds. I can include some of the backtraces from that if needed. On Wed, 2016-05-04 at 19:11 +0200, Daniel Vetter wrote: > 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 <cpaul@redhat.com> > 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
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 *)); } }
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 <cpaul@redhat.com> --- drivers/gpu/drm/drm_fb_helper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)