Patch "drm/i915/fbdev: Check for existence of ifbdev->vma before operations" has been added to the 4.12-stable tree

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

    drm/i915/fbdev: Check for existence of ifbdev->vma before operations

to the 4.12-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-i915-fbdev-check-for-existence-of-ifbdev-vma-before-operations.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Chris Wilson <[email protected]>
Date: Thu, 22 Jun 2017 17:02:11 +0100
Subject: drm/i915/fbdev: Check for existence of ifbdev->vma before operations

From: Chris Wilson <[email protected]>

commit 7581d5ca2bb269cfc2ce2d0cb489aac513167f6b upstream.

Commit fabef825626d ("drm/i915: Drop struct_mutex around frontbuffer flushes") adds a dependency to ifbdev->vma when flushing the framebufer, but the checks are only against the existence of the ifbdev->fb and not against ifbdev->vma. This leaves a window of opportunity where we may try to operate on the fbdev prior to it being probed (thanks to asynchronous booting).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101534

---
 drivers/gpu/drm/i915/intel_fbdev.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

@@ -535,13 +535,14 @@ static void intel_fbdev_destroy(struct i
 
 	drm_fb_helper_fini(&ifbdev->helper);
 
-	if (ifbdev->fb) {
+	if (ifbdev->vma) {
 		mutex_lock(&ifbdev->helper.dev->struct_mutex);
 		intel_unpin_fb_vma(ifbdev->vma);
 		mutex_unlock(&ifbdev->helper.dev->struct_mutex);
+	}
 
+	if (ifbdev->fb)
 		drm_framebuffer_remove(&ifbdev->fb->base);
-	}
 
 	kfree(ifbdev);
 }

@@ -765,7 +766,7 @@ void intel_fbdev_set_suspend(struct drm_
 	struct intel_fbdev *ifbdev = dev_priv->fbdev;
 	struct fb_info *info;
 
-	if (!ifbdev || !ifbdev->fb)
+	if (!ifbdev || !ifbdev->vma)
 		return;
 
 	info = ifbdev->helper.fbdev;

@@ -812,7 +813,7 @@ void intel_fbdev_output_poll_changed(str
 {
 	struct intel_fbdev *ifbdev = to_i915(dev)->fbdev;
 
-	if (ifbdev && ifbdev->fb)
+	if (ifbdev && ifbdev->vma)
 		drm_fb_helper_hotplug_event(&ifbdev->helper);
 }
 

@@ -824,7 +825,7 @@ void intel_fbdev_restore_mode(struct drm
 		return;
 
 	intel_fbdev_sync(ifbdev);
-	if (!ifbdev->fb)
+	if (!ifbdev->vma)
 		return;
 
 	if (drm_fb_helper_restore_fbdev_mode_unlocked(&ifbdev->helper) == 0)

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/drm-i915-fbdev-check-for-existence-of-ifbdev-vma-before-operations.patch