[PATCH] drm: Set vm_ops to GEM object's values during mmap

[Thomas Zimmermann]

The GEM mmap code relies on the GEM object's mmap callback to set the
VMA's vm_ops field. This is easily forgotten and lead to a memory leak
in the CMA helpers. Instead set the vm_ops field in the DRM core code
to the GEM object's value. Drivers with different needs can override
this in their mmap callback.

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Fixes: f5ca8eb6f9bd ("drm/cma-helper: Implement mmap as GEM CMA object functions")
Reported-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Eric Anholt <eric at anholt.net>
Cc: dri-devel at lists.freedesktop.org
---
 drivers/gpu/drm/drm_gem.c   | 23 ++++++++++++-----------
 drivers/gpu/drm/drm_prime.c |  4 ++++
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 34b2f111c01c..54d95621fcbb 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1069,27 +1069,28 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 
 	vma->vm_private_data = obj;
 
+	if (!obj->funcs->vm_ops) {
+		ret = -EINVAL;
+		goto err_drm_gem_object_put;
+	}
+	vma->vm_ops = obj->funcs->vm_ops;
+
 	if (obj->funcs->mmap) {
 		ret = obj->funcs->mmap(obj, vma);
-		if (ret) {
-			drm_gem_object_put(obj);
-			return ret;
-		}
+		if (ret)
+			goto err_drm_gem_object_put;
 		WARN_ON(!(vma->vm_flags & VM_DONTEXPAND));
 	} else {
-		if (obj->funcs->vm_ops)
-			vma->vm_ops = obj->funcs->vm_ops;
-		else {
-			drm_gem_object_put(obj);
-			return -EINVAL;
-		}
-
 		vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 		vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
 		vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
 	}
 
 	return 0;
+
+err_drm_gem_object_put:
+	drm_gem_object_put(obj);
+	return ret;
 }
 EXPORT_SYMBOL(drm_gem_mmap_obj);
 
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 683aa29ecd3b..0549ec190583 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -717,6 +717,10 @@ int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
 
 	if (obj->funcs && obj->funcs->mmap) {
+		if (!obj->funcs->vm_ops)
+			return -EINVAL;
+		vma->vm_ops = obj->funcs->vm_ops;
+
 		ret = obj->funcs->mmap(obj, vma);
 		if (ret)
 			return ret;
-- 
2.29.2