linux-cve-announce - CVE-2025-38673: Revert "drm/gem-framebuffer: Use dma

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Message-ID: <2025082202-CVE-2025-38673-80b9@gregkh>
Date: Fri, 22 Aug 2025 18:03:10 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38673: Revert "drm/gem-framebuffer: Use dma_buf from GEM object instance"

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

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

This reverts commit cce16fcd7446dcff7480cd9d2b6417075ed81065.

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

The Linux kernel CVE team has assigned CVE-2025-38673 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.15 with commit cce16fcd7446dcff7480cd9d2b6417075ed81065 and fixed in 6.15.9 with commit e31f5a1c2cd38bf977736cdfa79444e19d4005ec
	Issue introduced in 6.15 with commit cce16fcd7446dcff7480cd9d2b6417075ed81065 and fixed in 6.16 with commit 2712ca878b688682ac2ce02aefc413fc76019cd9

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-38673
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/gpu/drm/drm_gem_framebuffer_helper.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e31f5a1c2cd38bf977736cdfa79444e19d4005ec
	https://git.kernel.org/stable/c/2712ca878b688682ac2ce02aefc413fc76019cd9