linux-cve-announce - CVE-2022-49935: dma-buf/dma-resv: check if the new fence is really later

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Message-ID: <2025061847-CVE-2022-49935-bf21@gregkh>
Date: Wed, 18 Jun 2025 12:54:46 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49935: dma-buf/dma-resv: check if the new fence is really later

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

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

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

dma-buf/dma-resv: check if the new fence is really later

Previously when we added a fence to a dma_resv object we always
assumed the the newer than all the existing fences.

With Jason's work to add an UAPI to explicit export/import that's not
necessary the case any more. So without this check we would allow
userspace to force the kernel into an use after free error.

Since the change is very small and defensive it's probably a good
idea to backport this to stable kernels as well just in case others
are using the dma_resv object in the same way.

The Linux kernel CVE team has assigned CVE-2022-49935 to this issue.

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

	Fixed in 5.19.8 with commit c4c798fe98adceb642050819cb57cbc8f5c27870
	Fixed in 6.0 with commit a3f7c10a269d5b77dd5822ade822643ced3057f0

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-2022-49935
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/dma-buf/dma-resv.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/c4c798fe98adceb642050819cb57cbc8f5c27870
	https://git.kernel.org/stable/c/a3f7c10a269d5b77dd5822ade822643ced3057f0