CVE-2025-39927

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

ceph: fix race condition validating r_parent before applying state

Add validation to ensure the cached parent directory inode matches the

directory info in MDS replies. This prevents client-side race conditions

where concurrent operations (e.g. rename) cause r_parent to become stale

between request initiation and reply processing, which could lead to

applying state changes to incorrect directory inodes.

[ idryomov: folded a kerneldoc fixup and a follow-up fix from Alex to

move CEPH_CAP_PIN reference when r_parent is updated:

When the parent directory lock is not held, req->r_parent can become

stale and is updated to point to the correct inode. However, the

associated CEPH_CAP_PIN reference was not being adjusted. The

CEPH_CAP_PIN is a reference on an inode that is tracked for

accounting purposes. Moving this pin is important to keep the

accounting balanced. When the pin was not moved from the old parent

to the new one, it created two problems: The reference on the old,

stale parent was never released, causing a reference leak.

A reference for the new parent was never acquired, creating the risk

of a reference underflow later in ceph_mdsc_release_request(). This

patch corrects the logic by releasing the pin from the old parent and

acquiring it for the new parent when r_parent is switched. This

ensures reference accounting stays balanced. ]