CVE-2026-72471: fs/ntfs3: prevent potential lcn remains uninitialized

CVE-2026-72471: fs/ntfs3: prevent potential lcn remains uninitialized

[Greg Kroah-Hartman]

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

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

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

fs/ntfs3: prevent potential lcn remains uninitialized

The target VCN being sought was not found within runs[0], causing
run_lookup() to return false. This causes run_lookup_entry() to return
false, which in turn results in a len value of 0, and the new parameter
passed to attr_data_get_block() is NULL. Collectively, these factors
ultimately cause attr_data_get_block_locked() to exit prematurely without
initializing lcn, thereby triggering [1].

To prevent [1], the clen check within ni_seek_data_or_hole() has been
moved to occur before the lcn check.

[1]
BUG: KMSAN: uninit-value in ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]

The Linux kernel CVE team has assigned CVE-2026-72471 to this issue.


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

	Issue introduced in 7.0 with commit c61326967728392931f8a2240cb2cf4c81b523c1 and fixed in 7.1.5 with commit 7ae7e98b71438c494532492cbf58fc0d7f7988bb
	Issue introduced in 7.0 with commit c61326967728392931f8a2240cb2cf4c81b523c1 and fixed in 7.2-rc1 with commit 57ac2831c8e0f168090d38e3de758c6a59db44db

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-2026-72471
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/ntfs3/frecord.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/7ae7e98b71438c494532492cbf58fc0d7f7988bb
	https://git.kernel.org/stable/c/57ac2831c8e0f168090d38e3de758c6a59db44db