CVE-2025-39878

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.

Affected Software

References

• https://git.kernel.org/stable/c/249e0a47cdb46bb9eae65511c569044bd8698d7d
• https://git.kernel.org/stable/c/dd1616ecbea920d228c56729461ed223cc501425