We need to keep the reference to the drm_gem_object
until the last access by vkms_dumb_create.
Therefore, the put the object after it is used.
This fixes a use-after-free issue reported by syzbot.
While here, change vkms_gem_create() symbol to static.
Reported-and-tested-by: syzbot+e3372a2afe1e7ef04bc7@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
---
drivers/gpu/drm/vkms/vkms_drv.h | 5 -----
drivers/gpu/drm/vkms/vkms_gem.c | 11 ++++++-----
2 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index eda04ffba7b1..f4036bb0b9a8 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -117,11 +117,6 @@ struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
enum drm_plane_type type, int index);
/* Gem stuff */
-struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
- struct drm_file *file,
- u32 *handle,
- u64 size);
-
vm_fault_t vkms_gem_fault(struct vm_fault *vmf);
int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
index 2e01186fb943..c541fec57566 100644
--- a/drivers/gpu/drm/vkms/vkms_gem.c
+++ b/drivers/gpu/drm/vkms/vkms_gem.c
@@ -97,10 +97,10 @@ vm_fault_t vkms_gem_fault(struct vm_fault *vmf)
return ret;
}
-struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
- struct drm_file *file,
- u32 *handle,
- u64 size)
+static struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
+ struct drm_file *file,
+ u32 *handle,
+ u64 size)
{
struct vkms_gem_object *obj;
int ret;
@@ -113,7 +113,6 @@ struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
return ERR_CAST(obj);
ret = drm_gem_handle_create(file, &obj->gem, handle);
- drm_gem_object_put_unlocked(&obj->gem);
if (ret)
return ERR_PTR(ret);
@@ -142,6 +141,8 @@ int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
args->size = gem_obj->size;
args->pitch = pitch;
+ drm_gem_object_put_unlocked(gem_obj);
+
DRM_DEBUG_DRIVER("Created object of size %lld\n", size);
return 0;
--
2.26.0.rc2
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