CVE-2025-38669

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

Revert "drm/gem-shmem: Use dma_buf from GEM object instance"

This reverts commit 1a148af06000e545e714fe3210af3d77ff903c11.

The dma_buf field in struct drm_gem_object is not stable over the object instance's lifetime. The field becomes NULL when user space releases the final GEM handle on the buffer object. This resulted in a NULL-pointer deref.

Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer: Acquire internal references on GEM handles") only solved the problem partially. They especially don't work for buffer objects without a DRM framebuffer associated.

Hence, this revert to going back to using .import_attach->dmabuf.

v3:

• cc stable

A flaw in the DRM GEM shmem helpers could lead to a NULL pointer dereference when accessing obj->dma_buf after the last GEM handle was released. A local user with access to the DRM device could trigger a kernel crash by mapping or unmapping such an object.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.