[PATCH 3.8 060/166] drm/i915: Hold mutex across i915_gem_release

Kamal Mostafa
2014-01-15T21:51:14Z

From: Chris Wilson <chris@chris-wilson.co.uk>

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@anholt.net>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Kamal Mostafa <kamal@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 ef781e7..92896bf 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1794,8 +1794,10 @@ 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 a80bba9..e75cac6 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -310,10 +310,8 @@ 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