CyberRota Analysis
AI-GeneratedThe vulnerability affects the OpenRISC architecture within the Linux kernel, specifically related to improper synchronization of jump labels across symmetric multiprocessing (SMP) systems. This flaw can lead to stale instruction cache lines, potentially causing erratic behavior in applications relying on static keys after updates. Organizations utilizing OpenRISC systems should prioritize this patch to ensure system stability and prevent unexpected behavior in their applications.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: openrisc: Fix jump_label smp syncing The original commit 8c30b0018f9d ("openrisc: Add jump label support") copies from arm64 and does not properly consider how icache invalidation on remote cores works in OpenRISC. On OpenRISC remote icaches need to be invalidated otherwise static key's may remain state after updating. Fix SMP cache syncing by: 1. Properly invalidate remote core icaches on SMP systems by using icache_all_inv. The old code uses kick_all_cpus_sync() which runs a no-op IPI function call on remote CPU's which does execute a lot of code and flushes many cache lines in the process, but does not flush all and it's not correct on OpenRISC. 2. For architectures that do not have WRITETHROUGH caches be sure to flush the dcache after patching. To test this I first reproduced the issue using a custom test module [0]. The test confirmed that some icache lines maintained stale static_key code sequences after calling static_branch_enable(). After this patch there are no longer jump_label coherency issues. [0] https://github.com/stffrdhrn/or1k-utils/tree/master/tests/smp_static_key_test