CVE-2025-21893

Summary

CVE-2025-21893 is a vulnerability in the Linux kernel that affects the key management subsystem. The issue lies in the function key_put(), which attempts to reclaim quota too eagerly by checking if a key can be garbage collected based on its reference count. However, this check is performed after the key's usage has been reduced to zero, which is forbidden since the key may already have been destroyed by the garbage collector thread. To address this issue, the patch introduces a flag to indicate that a key is safe to be garbage collected, avoiding the need to check the reference count directly.

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