Executive Summary

This vulnerability exists in the Linux kernel's jitterentropy random number generator. The function jent_kcapi_random() serializes access to the shared jitterentropy state by holding a spinlock during the jent_read_entropy() call. Since this call involves expensive operations like jitter collection and SHA3 conditioning, holding a spinlock causes parallel readers to spin and wait, leading to stalls.

The fix replaces the long-held spinlock with a mutex, so that contended readers sleep instead of spinning. This prevents the non-preemptible lock hold and reduces contention and stalls during entropy generation.

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Impact Analysis

This vulnerability can cause performance degradation in systems using the Linux kernel's jitterentropy random number generator. Because parallel readers spin while waiting for the spinlock to be released during expensive entropy generation, it can lead to CPU stalls and reduced system responsiveness.

By replacing the spinlock with a mutex, the fix reduces CPU spinning and improves concurrency, preventing potential system slowdowns caused by contention on the entropy generation lock.

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Mitigation Strategies

This vulnerability in the Linux kernel involves a spinlock being held for a long time during entropy generation, which can cause stalls. The fix replaces the spinlock with a mutex to avoid non-preemptible lock holds.

To mitigate this vulnerability immediately, you should update your Linux kernel to a version where this issue is resolved, as the fix involves kernel code changes.

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