CVE-2026-74570: ntfs: harden runlist realloc size calculations

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

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

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

ntfs: harden runlist realloc size calculations

Add a shared helper to safely convert runlist element counts to byte sizes
using overflow checks, and use it in both ntfs_rl_realloc() and
ntfs_rl_realloc_nofail().

The Linux kernel CVE team has assigned CVE-2026-74570 to this issue.


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

	Issue introduced in 7.1 with commit 11ccc9107dc460de28af90fac1f42404d9802735 and fixed in 7.1.8 with commit 57e7b8bf7b02a0140463fea786e5172cbdf2da2f
	Issue introduced in 7.1 with commit 11ccc9107dc460de28af90fac1f42404d9802735 and fixed in 7.2-rc6 with commit 8bed376124ab4505b70083a2b91f2c7ef6d51e24

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-2026-74570
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:
	fs/ntfs/runlist.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/57e7b8bf7b02a0140463fea786e5172cbdf2da2f
	https://git.kernel.org/stable/c/8bed376124ab4505b70083a2b91f2c7ef6d51e24