CVE-2026-89658NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup

Official description

In the Linux kernel, the following vulnerability has been resolved: NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup nfs40_clean_admin_revoked() takes a stateid reference under clp->cl_lock, drops nn->client_lock, and calls nfsd4_drop_revoked_stid(), which dereferences the stateid's client through s->sc_client->cl_lock. The stateid reference does not pin the client, so a teardown racing the dropped lock can free the client while nfsd4_drop_revoked_stid() is still using it. This cleanup runs from the laundromat, so a periodic sweep can race force_expire_client() driven by a write to the clients/<id>/ctl file. Skip a client that is already expiring and otherwise pin it with cl_rpc_users under client_lock before dropping the lock, matching nfsd4_revoke_states().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/0ae0d2b5c5a1b39c0b3c15d96b32a5b0c583d519
• https://git.kernel.org/stable/c/b413ec5b23e3445dc9c4f273116078e2d4747626
• https://git.kernel.org/stable/c/81cf7f1413862f87b078920c838460a6a88aa030
• https://git.kernel.org/stable/c/7b4f8a1586c42d3afc3c0ac779af2db7ab1a5c55