linux-cve-announce - CVE-2025-39878: ceph: fix crash after fscrypt_encrypt_pagecache

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Message-ID: <2025092301-CVE-2025-39878-29db@gregkh>
Date: Tue, 23 Sep 2025 08:01:09 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39878: ceph: fix crash after fscrypt_encrypt_pagecache_blocks() error

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

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

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

ceph: fix crash after fscrypt_encrypt_pagecache_blocks() error

The function move_dirty_folio_in_page_array() was created by commit
ce80b76dd327 ("ceph: introduce ceph_process_folio_batch() method") by
moving code from ceph_writepages_start() to this function.

This new function is supposed to return an error code which is checked
by the caller (now ceph_process_folio_batch()), and on error, the
caller invokes redirty_page_for_writepage() and then breaks from the
loop.

However, the refactoring commit has gone wrong, and it by accident, it
always returns 0 (= success) because it first NULLs the pointer and
then returns PTR_ERR(NULL) which is always 0.  This means errors are
silently ignored, leaving NULL entries in the page array, which may
later crash the kernel.

The simple solution is to call PTR_ERR() before clearing the pointer.

The Linux kernel CVE team has assigned CVE-2025-39878 to this issue.

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

	Issue introduced in 6.15 with commit ce80b76dd32764cc914975777e058d4fae4f0ea0 and fixed in 6.16.8 with commit dd1616ecbea920d228c56729461ed223cc501425
	Issue introduced in 6.15 with commit ce80b76dd32764cc914975777e058d4fae4f0ea0 and fixed in 6.17-rc6 with commit 249e0a47cdb46bb9eae65511c569044bd8698d7d

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-2025-39878
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/ceph/addr.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/dd1616ecbea920d228c56729461ed223cc501425
	https://git.kernel.org/stable/c/249e0a47cdb46bb9eae65511c569044bd8698d7d