We implement automatic vma mmap() access management for all drivers using gem_mmap. We use the vma manager to add each open-file that creates a gem-handle to the vma-node of the underlying gem object. Once the handle is destroyed, we drop the open-file again.
This allows us to use drm_vma_node_is_allowed() on _any_ gem object to see whether an open-file is granted access. In drm_gem_mmap() we use this to verify that unprivileged users cannot guess gem offsets and map arbitrary buffers.
Note that this manages access for _all_ gem users (also TTM+GEM), but the actual access checks are only done for drm_gem_mmap(). TTM drivers use the TTM mmap helpers, which need to do that separately.
Signed-off-by: David Herrmann dh.herrmann@gmail.com --- drivers/gpu/drm/drm_gem.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index d6122ae..b2d59b2 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -298,6 +298,7 @@ drm_gem_handle_delete(struct drm_file *filp, u32 handle) spin_unlock(&filp->table_lock);
drm_gem_remove_prime_handles(obj, filp); + drm_vma_node_revoke(&obj->vma_node, filp->filp);
if (dev->driver->gem_close_object) dev->driver->gem_close_object(obj, filp); @@ -357,6 +358,11 @@ drm_gem_handle_create_tail(struct drm_file *file_priv, } *handlep = ret;
+ ret = drm_vma_node_allow(&obj->vma_node, file_priv->filp); + if (ret) { + drm_gem_handle_delete(file_priv, *handlep); + return ret; + }
if (dev->driver->gem_open_object) { ret = dev->driver->gem_open_object(obj, file_priv); @@ -701,6 +707,7 @@ drm_gem_object_release_handle(int id, void *ptr, void *data) struct drm_device *dev = obj->dev;
drm_gem_remove_prime_handles(obj, file_priv); + drm_vma_node_revoke(&obj->vma_node, file_priv->filp);
if (dev->driver->gem_close_object) dev->driver->gem_close_object(obj, file_priv); @@ -793,6 +800,10 @@ 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. * + * drm_gem_mmap_obj() assumes the user is granted access to the buffer while + * drm_gem_mmap() prevents unprivileged users from mapping random objects. So + * callers must verify access restrictions before calling this helper. + * * 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 @@ -841,6 +852,9 @@ EXPORT_SYMBOL(drm_gem_mmap_obj); * Look up the GEM object based on the offset passed in (vma->vm_pgoff will * contain the fake offset we created when the GTT map ioctl was called on * the object) and map it with a call to drm_gem_mmap_obj(). + * + * If the caller is not granted access to the buffer object, the mmap will fail + * with EACCES. Please see the vma manager for more information. */ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma) { @@ -861,6 +875,9 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma) if (!node) { mutex_unlock(&dev->struct_mutex); return drm_mmap(filp, vma); + } else if (!drm_vma_node_is_allowed(node, filp)) { + mutex_unlock(&dev->struct_mutex); + return -EACCES; }
obj = container_of(node, struct drm_gem_object, vma_node);