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 0F83943F085 for ; Mon, 7 Sep 2026 22:46:05 +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=1788821167; cv=none; b=YWzfd6KT+2fF7MVa0xoYvIoD2JbVCyzl986LNv/k0X+2L/nprhduq01ipEYQPwgIDOUjSxcO6/19dINp5AMF7ng2ulLWiwZigYfKySeuba+teVImLkpc/JblJRpdLB4vo2BK97qCiC7TnZ1jlJpmPO8uqiDZ4cPdWDNbRWRsqrA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788821167; c=relaxed/simple; bh=zHqyXH0TjXxHaPZVmViDVDE+Zoa5gxW4L32MF94AenU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a9z2Y1ijjRIKyXpIa4ON048+hT/K9nyyeaZTTigZehI08+NynhxZ7Dip8j5fv9k4OosHjJWZULHew49qf45yFBpjlqXy4/T9ew0OMvluPVZskBL5xTgg7K+jP9iTkZ3/nioG4eME+OhxJFggYiIUmoT4S6stUPiKT3SCQX1CrRw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cEIsQGvV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cEIsQGvV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42BE61F00A3A; Mon, 7 Sep 2026 22:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788821165; bh=e4opNrFM3cseW+NSJTBBZDcdl/Hhw1F8P1MlbB1jPH0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cEIsQGvVrttqQe41E4NrLbq4BTe9Zw5a1pTsZefqYHh9P3tlkGb1Ln8rKNSQjhyjZ bb/tEvDD/Rw3KZNq9HlYQzxsN7LUJqiJ/dworMDFZ/s+ogMdbEk4oMFhutlEqE398F 8wYF7zu0AfVQYZ7YUX3zhueOcvEqL+D1qAXl7aIFwdT91/br68bnraLx5JuvQXwNgi U6WQoR9SiBkqsADw2Q0GI99qUXKAEqenRFEgzguijEQfSkMyyJisskcyOJBcaBSWyK ylDHEwnS9sMRN37xedLbIsrbbYgBjLvzUoJG8D4nO/bqNFsDYScwigMB/XSQ75bruS RRHXgGGad6wtg== From: Sasha Levin To: stable@vger.kernel.org Cc: Chuck Lever , NeilBrown , Jeff Layton , Sasha Levin Subject: [PATCH 6.18.y 2/4] NFSD: Prevent client use-after-free during admin state revocation Date: Mon, 7 Sep 2026 18:46:01 -0400 Message-ID: <20260907224603.689417-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260907224603.689417-1-sashal@kernel.org> References: <2026090331-qualm-umbilical-2cdb@gregkh> <20260907224603.689417-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Stable-dep-of: 9026932ac8be ("NFSD: Prevent client use-after-free during blocked-lock reaping") Signed-off-by: Sasha Levin --- fs/nfsd/nfs4state.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index b24fc96b72fa0..3a0b91d1c9cc3 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1842,13 +1842,23 @@ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb) 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: @@ -1932,6 +1942,9 @@ void nfsd4_revoke_states(struct nfsd_net *nn, struct super_block *sb) */ 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; } } @@ -3218,6 +3231,11 @@ static void force_expire_client(struct nfs4_client *clp) 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); -- 2.53.0