Linux Kernel - AFS and RXRPC Peer Hash Locking Issue

CVE-2025-21809

Summary

A locking issue in the Linux kernel arises from the interaction between RXRPC and AFS, specifically in the peer hash locking mechanism. The vulnerability occurs during the cleanup process, where traditional spinlocks are used instead of BH-disabling locks. This mismatch can lead to deadlock scenarios, particularly if RXRPC operations are executed concurrently with RCU callbacks within the AFS module. Correcting this issue requires reverting to BH-disabling locks for RXRPC's peer hash management, thus ensuring safe locking behavior under different execution contexts.

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