CVE-2026-68434: serial: 8250_mid: Fix NULL function pointer dereference on DNV/ICX-D/SNR platforms

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

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

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

serial: 8250_mid: Fix NULL function pointer dereference on DNV/ICX-D/SNR platforms

Commit b1b4efea05a5 ("serial: 8250_mid: Disable DMA for selected
platforms") replaced the dnv_board setup and exit callbacks with
PTR_IF(false, ...), which evaluates to NULL. However, the three call
sites in mid8250_probe() and mid8250_remove() unconditionally
dereference these function pointers without NULL checks, causing a NULL
pointer dereference (kernel oops) on any Denverton (DNV), Ice Lake Xeon
D (ICX-D/CDF), or Snowridge (SNR) platform.

Fix this by adding the missing NULL checks before calling the setup and
exit callbacks.

The Linux kernel CVE team has assigned CVE-2026-68434 to this issue.


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

	Issue introduced in 6.6.145 with commit 587afb06a5d1dc5092d3d9e9ac3ccf22094d50c6 and fixed in 6.6.148 with commit 1096397c31f6bffa95e77bdd18fbca085be83e10
	Issue introduced in 6.12.96 with commit 977855894bca4b87afa50d21e3f3e85a5a0e901f and fixed in 6.12.101 with commit 600dcd548fb2b00a69f447684f52ba45d5a3540e
	Issue introduced in 6.18.39 with commit 1cd54e217c6e2cdb794a897b2f855e13ffcee586 and fixed in 6.18.42 with commit b2a3eeb57ba24f8a0e34a69d40adcc63e5b9ca56
	Issue introduced in 7.1.4 with commit 9690e8a342632344984af72bc56b7a1fba61e6cb and fixed in 7.1.6 with commit 8cbad52ccfa6a7f089cfab34979bc6cc3bff25be
	Issue introduced in 7.2-rc3 with commit b1b4efea05a56c0995e4702a86d6624b4fdff32f and fixed in 7.2-rc5 with commit 7fb13fd7e9a59a37cd911efff83abe19e3ee029d
	Issue introduced in 5.10.261 with commit 763d61ded752fbb3116efc951eff4363f237b7e0
	Issue introduced in 5.15.212 with commit c7d190bb07bf4e3b217c69370e94d1b4c80a40ad
	Issue introduced in 6.1.178 with commit 0b3ed3fa227ba778cabed96e7f8d84addb8bdf9c

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-2026-68434
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/tty/serial/8250/8250_mid.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/1096397c31f6bffa95e77bdd18fbca085be83e10
	https://git.kernel.org/stable/c/600dcd548fb2b00a69f447684f52ba45d5a3540e
	https://git.kernel.org/stable/c/b2a3eeb57ba24f8a0e34a69d40adcc63e5b9ca56
	https://git.kernel.org/stable/c/8cbad52ccfa6a7f089cfab34979bc6cc3bff25be
	https://git.kernel.org/stable/c/7fb13fd7e9a59a37cd911efff83abe19e3ee029d