CVE-2026-68176: tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

CVE-2026-68176: tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

[Greg Kroah-Hartman]

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

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

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

tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

If the mmio_pipe_open() fails to find a PCI device, the hiter->dev
will be assigned to NULL. The mmiotrace read() function dereferences the
hiter->dev if hiter exists.

Change the test of the read to not only check hiter being NULL, but also
the hiter->dev before dereferencing it.

The Linux kernel CVE team has assigned CVE-2026-68176 to this issue.


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

	Issue introduced in 2.6.27 with commit f984b51e0779a6dd30feedc41404013ca54e5d05 and fixed in 6.6.148 with commit faaf95135184208ee3ac6f33175c8d1800669dfc
	Issue introduced in 2.6.27 with commit f984b51e0779a6dd30feedc41404013ca54e5d05 and fixed in 6.12.101 with commit 201a01102c529772168181190cb084471082cf5c
	Issue introduced in 2.6.27 with commit f984b51e0779a6dd30feedc41404013ca54e5d05 and fixed in 6.18.42 with commit 8464427e1c177809a9488a97dfa2807d9dcf323b
	Issue introduced in 2.6.27 with commit f984b51e0779a6dd30feedc41404013ca54e5d05 and fixed in 7.1.6 with commit 724cd84b0546c07806840fa658714488553d13a2
	Issue introduced in 2.6.27 with commit f984b51e0779a6dd30feedc41404013ca54e5d05 and fixed in 7.2-rc5 with commit 144f29e85702234b23d2a62abf723e6a17eb5427

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-2026-68176
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:
	kernel/trace/trace_mmiotrace.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/faaf95135184208ee3ac6f33175c8d1800669dfc
	https://git.kernel.org/stable/c/201a01102c529772168181190cb084471082cf5c
	https://git.kernel.org/stable/c/8464427e1c177809a9488a97dfa2807d9dcf323b
	https://git.kernel.org/stable/c/724cd84b0546c07806840fa658714488553d13a2
	https://git.kernel.org/stable/c/144f29e85702234b23d2a62abf723e6a17eb5427