CVE-2025-39878

/// Technical 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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References