CVE-2026-74418: dma-fence: Fix potential tracepoint null pointer dereferences

From: Greg Kroah-Hartman <[email protected]>

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

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

dma-fence: Fix potential tracepoint null pointer dereferences

Trace_dma_fence_signaled, trace_dma_fence_wait_end and
trace_dma_fence_destroy can all currently dereference a null fence->ops
pointer after it has been reset on fence signalling.

Lets use the safe string getters for most tracepoints to avoid this class
of a problem, while for the signal tracepoint we move it to before ops are
cleared to avoid losing the driver and timeline name information. Apart
from moving it we also need to add a new tracepoint class to bypass the
safe name getters since the signaled bit is already set.

For dma_fence_init we also need to use the new tracepoint class since the
rcu read lock is not held there, and we can do the same for the enable
signaling since there we are certain the fence cannot be signaled while
we are holding the lock and have even validated the fence->ops.

The Linux kernel CVE team has assigned CVE-2026-74418 to this issue.


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

	Issue introduced in 7.1 with commit 541c8f2468b933acc5d129e84bd264923675a66e and fixed in 7.1.5 with commit 4e01fc9a5bc49b04fad403ffa71299b35e132ca8
	Issue introduced in 7.1 with commit 541c8f2468b933acc5d129e84bd264923675a66e and fixed in 7.2-rc1 with commit e94b9f01543cc6a83538c2c2cc645a424d3015ca

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-2026-74418
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-fence.c
	include/trace/events/dma_fence.h


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/4e01fc9a5bc49b04fad403ffa71299b35e132ca8
	https://git.kernel.org/stable/c/e94b9f01543cc6a83538c2c2cc645a424d3015ca