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 C095D3BFAE0; Fri, 4 Sep 2026 05:14:14 +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=1788498855; cv=none; b=c8eZKgRZgE772kC/vL71c9AqqEp4gmAl4IRW6t5Ynb0e+ujP3NUEbbHqck1VZJmVSXvizMk7d3fEzlS3v7m1LeaiLXGOnay0HVD14BhTrPrk4FHnbv+6kzl5q/w8j8S3A/H2RBG2gtiUgAz9zzWGu+r6YbOS/k13ySkTMGJkNDc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498855; c=relaxed/simple; bh=OR62eUGGd2z6qV5Mhxe0SvArp/FrWUsl9TetgkcpaRs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=px48q4vBemKEYLYZS+kGPoAnALOVr6A3C5H1hMgpKCbrT0kbIZqcWIiYEE+XegkETvcmDPAk/+rgM8nfAjFVmZsyy/6KRxS5ErBajLOIi0YAp8v2vRrC+UKMiGhx1Upg+x9lscP12ji2EBstvui+y6X2J1xJ26EI648RQQE/5kU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=N3TeEro9; 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="N3TeEro9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 271E91F00A3D; Fri, 4 Sep 2026 05:14:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788498854; bh=Dl68zU3wfsI4rjuvfF91bgeQHhQX9T/cCNnSGPxcd24=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=N3TeEro960my6ItU3d7DgUXtHBSzSbbiLf9GWkMNDUV0/0uaFRpESkjW9LmhONXej ukmNEwu3J46yh0+HRnxhWRv9EktLFai8Mcel1XOtfn62FD+fUe/hcOnFBARwHRTuR5 MOtrsRdBJRbxNCbBFvryyr7ASzq67eyORuhq79+Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, NeilBrown , Jeff Layton , Chuck Lever Subject: [PATCH 7.2 209/713] NFSD: Prevent client use-after-free during admin state revocation Date: Fri, 4 Sep 2026 06:52:57 +0200 Message-ID: <20260904045808.502496830@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045803.810145556@linuxfoundation.org> References: <20260904045803.810145556@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-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever commit e270e5a0778e5bff852c8862ce9576ce70359393 upstream. 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 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 @@ -1960,9 +1960,19 @@ 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) { + atomic_inc(&clp->cl_rpc_users); spin_unlock(&nn->client_lock); revoke_one_stid(nn, clp, stid); nfs4_put_stid(stid); @@ -1975,6 +1985,9 @@ 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; } } @@ -3347,6 +3360,11 @@ 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);