[3.11.y.z extended stable] Patch "drm/i915: Hold mutex across i915_gem_release" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    drm/i915: Hold mutex across i915_gem_release

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From f29111d418a1c294ee489697431b12b4dd47f2da Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Wed, 4 Dec 2013 14:52:06 +0000
Subject: drm/i915: Hold mutex across i915_gem_release

commit 0d1430a3f4b7cfd8779b78740a4182321f3ca7f3 upstream.

Inorder to serialise the closing of the file descriptor and its
subsequent release of client requests with i915_gem_free_request(), we
need to hold the struct_mutex in i915_gem_release(). Failing to do so
has the potential to trigger an OOPS, later with a use-after-free.

Testcase: igt/gem_close_race
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70874
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71029
Reported-by: Eric Anholt <eric at anholt.net>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/i915/i915_dma.c         | 2 ++
 drivers/gpu/drm/i915/i915_gem_context.c | 2 --
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index f466980..fc34376 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1831,8 +1831,10 @@ void i915_driver_lastclose(struct drm_device * dev)

 void i915_driver_preclose(struct drm_device * dev, struct drm_file *file_priv)
 {
+	mutex_lock(&dev->struct_mutex);
 	i915_gem_context_close(dev, file_priv);
 	i915_gem_release(dev, file_priv);
+	mutex_unlock(&dev->struct_mutex);
 }

 void i915_driver_postclose(struct drm_device *dev, struct drm_file *file)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 51b7a21..90b0491 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -335,10 +335,8 @@ void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;

-	mutex_lock(&dev->struct_mutex);
 	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
 	idr_destroy(&file_priv->context_idr);
-	mutex_unlock(&dev->struct_mutex);
 }

 static struct i915_hw_context *
--
1.8.3.2