Patch "drm/fb_helper: Fix references to dev->mode_config.num_connector" has been added to the 4.5-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    drm/fb_helper: Fix references to dev->mode_config.num_connector

to the 4.5-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-fb_helper-fix-references-to-dev-mode_config.num_connector.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>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
@@ -1899,7 +1899,6 @@ 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;
@@ -1918,7 +1917,7 @@ 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;
@@ -1964,7 +1963,7 @@ 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 *));
 		}
 	}


Patches currently in stable-queue which might be from cpaul@redhat.com are

queue-4.5/drm-i915-fbdev-fix-num_connector-references-in-intel_fb_initial_config.patch
queue-4.5/drm-i915-psr-try-to-program-link-training-times-correctly.patch
queue-4.5/drm-fb_helper-fix-references-to-dev-mode_config.num_connector.patch
queue-4.5/drm-atomic-verify-connector-funcs-null-when-clearing-states.patch