CVE-2026-89667

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

nfsd: close shrinker/GC/fsnotify vs per-net shutdown race in filecache

The shrinker, GC worker, and fsnotify/lease callbacks can unhash an nfsd_file from the rhashtable and then call nfsd_file_dispose_list_delayed() to move it to the per-net dispose list. If nfsd_file_cache_shutdown_net() runs concurrently, its rhashtable walk misses the already-unhashed file, and its drain of the per-net dispose list can run before the file has been queued. The file then sits on the per-net list with no thread to drain it, leaking both the file and its associated state.

The GC worker and shrinker already hold nfsd_gc_lock while walking the LRU, but in the original code they release it before calling nfsd_file_dispose_list_delayed(). The fsnotify/lease path (nfsd_file_close_inode) has no synchronization at all.

Fix this by:

1. Widening nfsd_gc_lock in both nfsd_file_gc() and nfsd_file_lru_scan() to cover the nfsd_file_dispose_list_delayed() call.

2. Wrapping nfsd_file_close_inode() in nfsd_gc_lock so that all three callers of nfsd_file_dispose_list_delayed() hold the lock.

3. Adding a spin_lock/unlock(nfsd_gc_lock) barrier in nfsd_file_cache_shutdown_net() after the purge, so that any in-progress disposal has fully completed before the per-net list is drained.

All operations inside the lock are non-sleeping (rhashtable lookups, atomic bit/refcount ops, list moves, svc_wake_up), so the spinlock is appropriate.

Affected Software

References

• https://git.kernel.org/stable/c/08af9593e2b472fd98c00faf1bf03bdbb7203477
• https://git.kernel.org/stable/c/40162cfea79b9510380decfdd1795b754dc9f972
• https://git.kernel.org/stable/c/6d6b9f6a75c3767250e9c23ace4e384ab8f7843e
• https://git.kernel.org/stable/c/b15997b53b61c74fb4d083f7261d19f389ff854f