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authorLyude <cpaul@redhat.com>2016-05-12 10:56:59 -0400
committerDaniel Vetter <daniel.vetter@ffwll.ch>2016-05-17 15:44:41 +0200
commit255f0e7c418ad95a4baeda017ae6182ba9b3c423 (patch)
tree6363607e632a4253db295a9b9d3becce37a5146a
parent14a3842a1d5945067d1dd0788f314e14d5b18e5b (diff)
drm/fb_helper: Fix references to dev->mode_config.num_connectortopic/drm-misc-2016-05-17
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. Cc: stable@vger.kernel.org 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
-rw-r--r--drivers/gpu/drm/drm_fb_helper.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index e03f8ad90b3a..7c2eb75db60f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1968,7 +1968,6 @@ 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;
const struct drm_connector_helper_funcs *connector_funcs;
struct drm_encoder *encoder;
@@ -1987,7 +1986,7 @@ 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;
@@ -2033,7 +2032,7 @@ 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 *));
}
}

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