SELinux avdcache Permission Check Auditing Flaw

Executive Summary

This vulnerability in the Linux kernel involves incorrect handling of auditing for SELinux permission checks. The per-task avdcache was saving and reusing an audited vector that was not properly updated based on current permissions or distinguishing between denied and allowed cases. This led to some permission checks, such as directory write checks after a cached directory search, not being audited correctly.

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Detection Guidance

This vulnerability is specific to the Linux kernel's SELinux auditing mechanism. Detection requires checking kernel logs for missing or incorrect permission audit entries related to directory operations. Examine audit logs for events where write permissions were not logged after a search permission check on the same directory. Use commands like 'ausearch -m avc' or 'journalctl -t audit' to review SELinux audit logs for inconsistencies in permission checks.

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Impact Analysis

This vulnerability could impact you by allowing unauthorized or suspicious activities to go undetected in systems using SELinux. Since auditing is a critical security feature, incorrect auditing may result in missed security events, making it harder to investigate breaches or policy violations.

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Compliance Impact

This vulnerability may affect compliance with standards requiring detailed audit logs, such as GDPR and HIPAA. If permission checks are not audited correctly, organizations may fail to maintain required records of access and activities, leading to potential compliance violations and legal risks.

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Mitigation Strategies

Update your Linux kernel to the latest patched version to resolve the selinux avdcache auditing issue. Monitor system logs for any unusual permission denials or audit failures after applying the update.

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