From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 10BEC53A887; Wed, 9 Sep 2026 14:39:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964770; cv=none; b=aJwgveVMElkmpPxten/iKGlxk4Ove2LvAt2c58JyYH6HoJ2GjsctF9NSnCHfhetb79tY79ocJbwOVe2IkmCOeDBP09ydhwUL06XC1HLe5eIWGOrtzZ5latlVr01cazf1nwkUAt8cGq4HxELv+JM6BnZg9/J27Dix8q/5s+Mehbs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964770; c=relaxed/simple; bh=jHWAMnJMYtQQEXK6e6cugHRvCLE/3+7YTob1NbH1iJk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=U7hBkSTDgjl+iKuBP8bFbcVDvpYOaas+AH2mR+34jzPeumRXTZMT4AuWfkOK1VemNQbNfaOiapMDDV9U4Zb1OFezT1POPeJIyQObbMaWa0tvd02h2Bpf6T9GFMRSlYVipFHah0+1q8KXaARkFSt3hMwuUsnXNuzTTNBV940gAH0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1I5H/IT1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1I5H/IT1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6B96F1F00A3D; Wed, 9 Sep 2026 14:39:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788964769; bh=Wgl9G9vyzlrlZwFrzc59/lxOuV99z9Uk2Fl8/bEW8vw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1I5H/IT1hQNsx41BdqwZVdl+ZGbVubxTCUlKVTGnBfs8IkqlEMGahIHqSaUIRfg/v RIqoa9OSvUflzIEERGhjx0HnAJH5KZ6VM5no+fwNYvMHEcB4+lCLgpVL5DpiwU1ToI 2kyF+F8HFwwiw29to1O4WboI5GT/LupFSwRDKTZE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, NeilBrown , Jeff Layton , Chuck Lever , Sasha Levin Subject: [PATCH 6.18 537/583] NFSD: Prevent client use-after-free during admin state revocation Date: Wed, 9 Sep 2026 15:43:42 +0200 Message-ID: <20260909134256.381524935@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134237.773280130@linuxfoundation.org> References: <20260909134237.773280130@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever [ Upstream commit e270e5a0778e5bff852c8862ce9576ce70359393 ] A stateid holds only a bare pointer to its nfs4_client; a stateid reference does not pin it. The client survives only because __destroy_client() drains its stateids before free_client() runs. nfsd4_revoke_states() drops nn->client_lock across revoke_one_stid(), which dereferences the client to revoke a stateid and read clp->cl_minorversion. A teardown racing the dropped lock can free the client first. Pinning cl_rpc_users under client_lock blocks the DESTROY_CLIENTID and EXCHANGE_ID teardown, which refuses while cl_rpc_users is non-zero. force_expire_client() ignores it: once its wait for cl_rpc_users to reach zero has passed, a later pin goes unnoticed. Under client_lock, skip a client whose cl_time is already zero -- force_expire_client() clears it there before waiting -- otherwise pin cl_rpc_users before dropping the lock. The walk then either sees the expiry and skips, or pins in time for that wait to cover the revoke. Fixes: 1c13bf9f2e3c ("nfsd: allow lock state ids to be revoked and then freed") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260709-cel-v4-3-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever [ adapted revoke_one_stid() calls to the branch’s inline revocation logic ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/nfs4state.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1841,13 +1841,23 @@ void nfsd4_revoke_states(struct nfsd_net struct nfs4_client *clp; retry: list_for_each_entry(clp, head, cl_idhash) { - struct nfs4_stid *stid = find_one_sb_stid(clp, sb, - sc_types); + struct nfs4_stid *stid; + + /* + * force_expire_client() ignores cl_rpc_users once + * its wait_event() has passed, so pinning cannot + * keep an already-expiring client alive; the + * expiry path revokes its states instead. + */ + if (is_client_expired(clp)) + continue; + stid = find_one_sb_stid(clp, sb, sc_types); if (stid) { struct nfs4_ol_stateid *stp; struct nfs4_delegation *dp; struct nfs4_layout_stateid *ls; + atomic_inc(&clp->cl_rpc_users); spin_unlock(&nn->client_lock); switch (stid->sc_type) { case SC_TYPE_OPEN: @@ -1931,6 +1941,9 @@ void nfsd4_revoke_states(struct nfsd_net */ nn->nfs40_last_revoke = ktime_get_boottime_seconds(); + if (atomic_dec_and_test(&clp->cl_rpc_users) && + is_client_expired(clp)) + wake_up_all(&expiry_wq); goto retry; } } @@ -3217,6 +3230,11 @@ static void force_expire_client(struct n trace_nfsd_clid_admin_expired(&clp->cl_clientid); + /* + * cl_time is cleared under client_lock before the wait so a + * revocation walk pinning cl_rpc_users under it either skips + * this client or is seen by this wait_event(). + */ spin_lock(&nn->client_lock); clp->cl_time = 0; spin_unlock(&nn->client_lock);