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.