linux-cve-announce - CVE-2025-40241: erofs: fix crafted invalid cases for encoded extents

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Message-ID: <2025120403-CVE-2025-40241-c6ed@gregkh>
Date: Thu,  4 Dec 2025 16:32:16 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40241: erofs: fix crafted invalid cases for encoded extents

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

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

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

erofs: fix crafted invalid cases for encoded extents

Robert recently reported two corrupted images that can cause system
crashes, which are related to the new encoded extents introduced
in Linux 6.15:

  - The first one [1] has plen != 0 (e.g. plen == 0x2000000) but
    (plen & Z_EROFS_EXTENT_PLEN_MASK) == 0. It is used to represent
    special extents such as sparse extents (!EROFS_MAP_MAPPED), but
    previously only plen == 0 was handled;

  - The second one [2] has pa 0xffffffffffdcffed and plen 0xb4000,
    then "cur [0xfffffffffffff000] += bvec.bv_len [0x1000]" in
    "} while ((cur += bvec.bv_len) < end);" wraps around, causing an
    out-of-bound access of pcl->compressed_bvecs[] in
    z_erofs_submit_queue().  EROFS only supports 48-bit physical block
    addresses (up to 1EiB for 4k blocks), so add a sanity check to
    enforce this.

The Linux kernel CVE team has assigned CVE-2025-40241 to this issue.


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

	Issue introduced in 6.15 with commit 1d191b4ca51d73699cb127386b95ac152af2b930 and fixed in 6.17.6 with commit 00d8fe0b72f4ca0a983abced36aad2160038c421
	Issue introduced in 6.15 with commit 1d191b4ca51d73699cb127386b95ac152af2b930 and fixed in 6.18 with commit a429b76114aaca3ef1aff4cd469dcf025431bd11

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-2025-40241
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/00d8fe0b72f4ca0a983abced36aad2160038c421
	https://git.kernel.org/stable/c/a429b76114aaca3ef1aff4cd469dcf025431bd11