CVE-2026-89658

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().