CVE-2026-89660

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> NFSD: Prevent client use-after-free during admin state revocation<br /> <br /> A stateid holds only a bare pointer to its nfs4_client; a stateid<br /> reference does not pin it. The client survives only because<br /> __destroy_client() drains its stateids before free_client() runs.<br /> <br /> nfsd4_revoke_states() drops nn-&gt;client_lock across revoke_one_stid(),<br /> which dereferences the client to revoke a stateid and read<br /> clp-&gt;cl_minorversion. A teardown racing the dropped lock can free<br /> the client first.<br /> <br /> Pinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and<br /> EXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero.<br /> force_expire_client() ignores it: once its wait for cl_rpc_users to<br /> reach zero has passed, a later pin goes unnoticed.<br /> <br /> Under client_lock, skip a client whose cl_time is already zero --<br /> force_expire_client() clears it there before waiting -- otherwise pin<br /> cl_rpc_users before dropping the lock. The walk then either sees the<br /> expiry and skips, or pins in time for that wait to cover the revoke.