KEYS: Fix add_key() race with keyring restriction

Summary

In the Linux kernel, the following vulnerability has been resolved: KEYS: Fix add_key() race with keyring restriction __key_create_or_update() snapshots keyring->restrict_link before taking the destination keyring's semaphore. keyring_restrict() installs a restriction while holding that semaphore. This allows a writer to observe no restriction, wait for the keyring owner to install a reject-all restriction and return successfully, and then link a key using the stale NULL snapshot. The writer only needs write permission on the destination keyring. Move the restrict_link read after __key_link_lock() and __key_link_begin(). The read and the subsequent restriction check are then serialized with restriction installation by keyring->sem. The race was reproduced on v7.2.8 in 19 executions where restriction installation returned before the link completed. All 19 linked the key despite the reject-all restriction. With this change, 312 executions reached the same ordering and every add_key() call failed with -EPERM. The issue was found by manual concurrency analysis assisted by AI-based analysis and independently verified with a QEMU reproducer and kernel instrumentation.

Timeline

1. Oct 23, 2026, 12:21 PM UTCCVE published
2. Oct 23, 2026, 12:45 PM UTCFirst seen by cve.now
3. Oct 30, 2026, 12:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  4.7

• KernelLinux

  From 4.7.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.113; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.11

References 8