drm/virtio: fix object leak when drm_gem_handle_create() fails

Overview

In the Linux kernel, the following vulnerability has been resolved:

drm/virtio: fix object leak when drm_gem_handle_create() fails

virtio_gpu_gem_create() owns the reference taken by virtio_gpu_object_create(). On the drm_gem_handle_create() error path it calls drm_gem_object_release() instead of dropping that reference.

drm_gem_object_release() is the inverse of drm_gem_object_init() and does not touch the reference count or call obj->funcs->free(), so it is only correct as the last step of a destructor, as in virtio_gpu_cleanup_object(). Using it here leaves the bo at refcount 1 with no remaining reference, so virtio_gpu_free_object() never runs and the shmem pages, sg table and virtio_gpu_object are leaked. Since virtio_gpu_object_create() has already set bo->created, VIRTIO_GPU_CMD_RESOURCE_UNREF is not queued either, leaking the host-side resource and the resource id.

drm_gem_handle_create_tail() drops the handle reference on all of its internal error paths, so the caller only has to drop its own. Use drm_gem_object_put(), matching the success path below.

Affected

• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < 13423a058187c2039aa8cb235c916be4477221b7
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < 687be2f8b5e0e0ca9a7028f8f6413d0ed3fbb9dc
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < 264ae8ac8fd625b6c118baf16c111adeee2ec632
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < e2edd2d78d2cf8446de017adec9598feefed3297
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < 372e9c3d45f664a2c000427ccbf6cdc2f99b3170
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < a93dce15dfef200c346b050a2acbed516cc62706
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < f75066c79d1eec453c0d386ef8636873d1e11f2c
• Linux >= dc5698e80cf724770283e10414054662bdf6ccfa < 36570ef2244cc4d7563b1f0157bc0f032498638c
• Linux 4.2

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.