CVE-2026-31400sunrpc: fix cache_request leak in cache_release

Official description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix cache_request leak in cache_release When a reader's file descriptor is closed while in the middle of reading a cache_request (rp->offset != 0), cache_release() decrements the request's readers count but never checks whether it should free the request. In cache_read(), when readers drops to 0 and CACHE_PENDING is clear, the cache_request is removed from the queue and freed along with its buffer and cache_head reference. cache_release() lacks this cleanup. The only other path that frees requests with readers == 0 is cache_dequeue(), but it runs only when CACHE_PENDING transitions from set to clear. If that transition already happened while readers was still non-zero, cache_dequeue() will have skipped the request, and no subsequent call will clean it up. Add the same cleanup logic from cache_read() to cache_release(): after decrementing readers, check if it reached 0 with CACHE_PENDING clear, and if so, dequeue and free the cache_request.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1dfedb293943e491379c9302b428e6f920a73d12
• https://git.kernel.org/stable/c/f18c1f2a88ca91357916997cdb0f7adaf14fc497
• https://git.kernel.org/stable/c/7bcd5e318876ac638c8ceade7a648e76ac8c48e1
• https://git.kernel.org/stable/c/41f6ba6c98a618043d2cd71030bf9a752dfab8b2
• https://git.kernel.org/stable/c/301670dcd098c1fe5c2fe90fb3c7a8f4814d2351
• https://git.kernel.org/stable/c/be5c35960e5ead70862736161836e2d1bc7352dc
• https://git.kernel.org/stable/c/373457de14281c1fc7cace6fc4c8a267fc176673
• https://git.kernel.org/stable/c/17ad31b3a43b72aec3a3d83605891e1397d0d065