CVE-2026-89682

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

nfsd: fix fcache disposal UAF by inlining dispose state into nfsd net

nfsd file dispose list delayed() defers fput() to nfsd service threads via a per-net freeme queue, preventing the shrinker and GC worker from bearing the cost of closing files (see ffb402596147). However, the queue lives in a separately-allocated struct nfsd fcache disposal that is freed by nfsd free fcache disposal net() during per-net teardown. The global shrinker, laundrette, and fsnotify callbacks can still be inside nfsd file dispose list delayed() dereferencing that pointer, causing a use-after-free.

Inline the spinlock and freeme list directly into struct nfsd net (as fcache dispose lock and fcache dispose list), eliminating the separately allocated struct nfsd fcache disposal entirely. These fields now have the same lifetime as the net namespace itself, so there is no dangling pointer to chase.

nfsd file cache start net() now just initializes the inline fields and cannot fail due to allocation. nfsd file cache shutdown net() drains the inline list directly instead of freeing a separate struct. The alloc/free helpers are removed.