| From 255f0e7c418ad95a4baeda017ae6182ba9b3c423 Mon Sep 17 00:00:00 2001 |
| From: Lyude <cpaul@redhat.com> |
| Date: Thu, 12 May 2016 10:56:59 -0400 |
| Subject: drm/fb_helper: Fix references to dev->mode_config.num_connector |
| |
| From: Lyude <cpaul@redhat.com> |
| |
| commit 255f0e7c418ad95a4baeda017ae6182ba9b3c423 upstream. |
| |
| 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. |
| |
| Note: This is just polish for 4.7, Dave Airlie's drm_connector |
| refcounting fixed these bugs for real. But it's good enough duct-tape |
| for stable kernel backporting, since backporting the refcounting |
| changes is way too invasive. |
| |
| Signed-off-by: Lyude <cpaul@redhat.com> |
| [danvet: Clarify why we need this. Also remove the now unused "dev" |
| local variable to appease gcc.] |
| Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
| Link: http://patchwork.freedesktop.org/patch/msgid/1463065021-18280-3-git-send-email-cpaul@redhat.com |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/gpu/drm/drm_fb_helper.c | 5 ++--- |
| 1 file changed, 2 insertions(+), 3 deletions(-) |
| |
| --- a/drivers/gpu/drm/drm_fb_helper.c |
| +++ b/drivers/gpu/drm/drm_fb_helper.c |
| @@ -1895,7 +1895,6 @@ static int drm_pick_crtcs(struct drm_fb_ |
| int n, int width, int height) |
| { |
| int c, o; |
| - struct drm_device *dev = fb_helper->dev; |
| struct drm_connector *connector; |
| const struct drm_connector_helper_funcs *connector_funcs; |
| struct drm_encoder *encoder; |
| @@ -1914,7 +1913,7 @@ static int drm_pick_crtcs(struct drm_fb_ |
| 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 +1959,7 @@ static int drm_pick_crtcs(struct drm_fb_ |
| 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 *)); |
| } |
| } |