From: Lyude <cp...@redhat.com> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== 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 <cp...@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.vet...@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1463065021-18280-3-git-send-email-cp...@redhat.com Signed-off-by: Jiri Slaby <jsl...@suse.cz> --- drivers/gpu/drm/drm_fb_helper.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 49557c957be8..1965b8963606 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1359,7 +1359,6 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper, int n, int width, int height) { int c, o; - struct drm_device *dev = fb_helper->dev; struct drm_connector *connector; struct drm_connector_helper_funcs *connector_funcs; struct drm_encoder *encoder; @@ -1380,7 +1379,7 @@ 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; @@ -1427,7 +1426,7 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper, best_crtc = crtc; best_score = score; memcpy(best_crtcs, crtcs, - dev->mode_config.num_connector * + fb_helper->connector_count * sizeof(struct drm_fb_helper_crtc *)); } } -- 2.9.0
