CVE-2026-53015: erofs: unify lcn as u64 for 32-bit platforms

CVE-2026-53015: erofs: unify lcn as u64 for 32-bit platforms

[Greg Kroah-Hartman]

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

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

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

erofs: unify lcn as u64 for 32-bit platforms

As sashiko reported [1], `lcn` was typed as `unsigned long` (or
`unsigned int` sometimes), which is only 32 bits wide on 32-bit
platforms, which causes `(lcn << lclusterbits)` to be truncated
at 4 GiB.

In order to consolidate the logic, just use `u64` consistently
around the codebase.

[1] https://sashiko.dev/r/20260420034612.1899973-1-hsiangkao%40linux.alibaba.com

The Linux kernel CVE team has assigned CVE-2026-53015 to this issue.


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

	Issue introduced in 5.3 with commit 152a333a589560bee002e4c96761f1b560a5793c and fixed in 6.12.91 with commit 4fc9b12e43a3f19a01a8fb61f7961be79de20253
	Issue introduced in 5.3 with commit 152a333a589560bee002e4c96761f1b560a5793c and fixed in 6.18.33 with commit 858e4d98a86adf34584767388deb6c9b217f70c5
	Issue introduced in 5.3 with commit 152a333a589560bee002e4c96761f1b560a5793c and fixed in 7.0.10 with commit 582b0bf201157632cb5474c885989a6ebda46521
	Issue introduced in 5.3 with commit 152a333a589560bee002e4c96761f1b560a5793c and fixed in 7.1 with commit 2d8c7edcb661812249469f4a5b62e9339118846f

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-2026-53015
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/erofs/zmap.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/4fc9b12e43a3f19a01a8fb61f7961be79de20253
	https://git.kernel.org/stable/c/858e4d98a86adf34584767388deb6c9b217f70c5
	https://git.kernel.org/stable/c/582b0bf201157632cb5474c885989a6ebda46521
	https://git.kernel.org/stable/c/2d8c7edcb661812249469f4a5b62e9339118846f