[PATCH v2] drm/gem: add mutex lock when using drm_gem_mmap_obj

[Seung-Woo Kim]

From: YoungJun Cho <yj44.cho at samsung.com>

The drm_gem_mmap_obj() has to be protected with dev->struct_mutex,
but some caller functions do not. So it adds mutex lock to missing
callers and adds assertion to check whether drm_gem_mmap_obj() is
called with mutex lock or not.

Signed-off-by: YoungJun Cho <yj44.cho at samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
CC: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
CC: Rob Clark <robdclark at gmail.com>
---
This patch is based on drm-next branch.

Changes since v1:
- Use lockdep_assert_held() instead of mutex_is_locked() as Maarten commented
- Fix commit message about assertion

 drivers/gpu/drm/drm_gem.c                 |    4 ++++
 drivers/gpu/drm/drm_gem_cma_helper.c      |    3 +++
 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c |    3 +++
 3 files changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 4321713..34c0be7 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -661,6 +661,8 @@ EXPORT_SYMBOL(drm_gem_vm_close);
  * the GEM object is not looked up based on its fake offset. To implement the
  * DRM mmap operation, drivers should use the drm_gem_mmap() function.
  *
+ * NOTE: This function has to be protected with dev->struct_mutex
+ *
  * Return 0 or success or -EINVAL if the object size is smaller than the VMA
  * size, or if no gem_vm_ops are provided.
  */
@@ -669,6 +671,8 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 {
 	struct drm_device *dev = obj->dev;
 
+	lockdep_assert_held(&dev->struct_mutex);
+
 	/* Check for valid size. */
 	if (obj_size < vma->vm_end - vma->vm_start)
 		return -EINVAL;
diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index 9efabce..ce06397 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -487,9 +487,12 @@ static int drm_gem_cma_dmabuf_mmap(struct dma_buf *dmabuf,
 {
 	struct drm_gem_cma_object *cma_obj = dmabuf->priv;
 	struct drm_gem_object *gem_obj = &cma_obj->base;
+	struct drm_device *dev = gem_obj->dev;
 	int ret;
 
+	mutex_lock(&dev->struct_mutex);
 	ret = drm_gem_mmap_obj(gem_obj, gem_obj->size, vma);
+	mutex_unlock(&dev->struct_mutex);
 	if (ret < 0)
 		return ret;
 
diff --git a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
index 3256693..4fcca8d 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
@@ -140,12 +140,15 @@ static int omap_gem_dmabuf_mmap(struct dma_buf *buffer,
 		struct vm_area_struct *vma)
 {
 	struct drm_gem_object *obj = buffer->priv;
+	struct drm_device *dev = obj->dev;
 	int ret = 0;
 
 	if (WARN_ON(!obj->filp))
 		return -EINVAL;
 
+	mutex_lock(&dev->struct_mutex);
 	ret = drm_gem_mmap_obj(obj, omap_gem_mmap_size(obj), vma);
+	mutex_unlock(&dev->struct_mutex);
 	if (ret < 0)
 		return ret;
 
-- 
1.7.9.5