CVE-2026-89548 — SUNRPC: always drain cache_cleaner before destroying a cache_detail

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

SUNRPC: always drain cache_cleaner before destroying a cache_detail

sunrpc_destroy_cache_detail() only cancels the global cache_cleaner delayed_work when cache_list is empty. During per-netns teardown cache_list is never empty because init_net's caches remain registered, so the cancel never fires. After unlink, the caller proceeds to cache_destroy_net() which kfrees the cache_detail while cache_clean() may still hold a dangling pointer to it. The result is a use-after-free: cache_dequeue() takes cd->queue_lock on freed memory, and cache_put() dereferences cd->cache_put as a function pointer from freed slab.

Drop the list_empty guard so that cancel_delayed_work_sync() always runs, ensuring any in-flight cache_clean() completes before the cache_detail is freed. Re-arm the cleaner afterwards if other caches are still registered.

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CVE-2026-89548 — SUNRPC: always drain cache_cleaner before destroying a cache_detail