CVE-2026-80963: dm-stats: fix a crash if allocation of per-cpu data fails

CVE-2026-80963: dm-stats: fix a crash if allocation of per-cpu data fails

[Greg Kroah-Hartman]

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

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

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

dm-stats: fix a crash if allocation of per-cpu data fails

If "dm_kvzalloc(percpu_alloc_size, cpu_to_node(cpu))" fails, the code
jumps to the "out" label and calls dm_stat_free. dm_stat_free does
"for_each_possible_cpu(cpu) { dm_kvfree(s->stat_percpu[cpu][0].histogram,
s->histogram_alloc_size);", which crashes with NULL pointer dereference
if s->stat_percpu[cpu] is NULL.

This commit fixes the bug by testing s->stat_percpu[cpu] for NULL before
using it.

The Linux kernel CVE team has assigned CVE-2026-80963 to this issue.


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

	Issue introduced in 3.12 with commit fd2ed4d252701d3bbed4cd3e3d267ad469bb832a and fixed in 6.12.109 with commit c3f211b7a277dd404b4e7d23095be964b5b46a27
	Issue introduced in 3.12 with commit fd2ed4d252701d3bbed4cd3e3d267ad469bb832a and fixed in 6.18.50 with commit 74210fa072960a18bb0eead487585452af722e4f
	Issue introduced in 3.12 with commit fd2ed4d252701d3bbed4cd3e3d267ad469bb832a and fixed in 7.2.4 with commit 0c8f7870ed3ebd512f090d7714cc2c556b9e5c75
	Issue introduced in 3.12 with commit fd2ed4d252701d3bbed4cd3e3d267ad469bb832a and fixed in 7.3-rc1 with commit cc87e26d9cce22061dc21e51e11afef29dbbc36a

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-2026-80963
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/md/dm-stats.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/c3f211b7a277dd404b4e7d23095be964b5b46a27
	https://git.kernel.org/stable/c/74210fa072960a18bb0eead487585452af722e4f
	https://git.kernel.org/stable/c/0c8f7870ed3ebd512f090d7714cc2c556b9e5c75
	https://git.kernel.org/stable/c/cc87e26d9cce22061dc21e51e11afef29dbbc36a