Policycoreutils: policycoreutils: toctou race condition in fixfiles allows arbitrary selinux label manipulation

Overview

A TOCTOU (Time-of-Check-Time-of-Use) race condition vulnerability was found in the fixfiles script in policycoreutils. When running fixfiles relabel or fixfiles restore, the script used find and chcon commands to locate and relabel unlabeled files under /tmp and other directories. A local attacker could exploit a race window between the file discovery and the label change operation by swapping directory components with symlinks, causing chcon to follow the symlink and modify SELinux labels on arbitrary system files. This could undermine SELinux mandatory access control protections on critical files such as /etc/shadow.

Affected

• policycoreutils-main (all versions)
• policycoreutils (all versions)
• policycoreutils
• policycoreutils (all versions)
• policycoreutils (all versions)
• policycoreutils (all versions)
• openshift/ose-rhel-coreos-8 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

As a workaround, use 'restorecon -R /' directly instead of 'fixfiles relabel' or 'fixfiles restore' to perform filesystem relabeling. This avoids the vulnerable /tmp-specific find+chcon code path entirely. Note that this skips the /tmp cleanup logic, but on modern systems where /tmp is mounted as tmpfs, this cleanup is unnecessary as tmpfs cannot retain files from a prior boot.