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 79B50576EB5; Wed, 9 Sep 2026 14:39:26 +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=1788964767; cv=none; b=twqv1dhEhrOrBmUIQkDwLsavVg9ygs5MoecIa/URUSslGpw0j/c8pRn3ptcf5mfLtqM8DQgyW6riNhM+XO7YM+7Mer8mrNAZFatkmWYZSz1RYCKP9VpleQBk1zdD7o9Ev2hZKETVDOx+K1St26ILno63Llturt3FtQTOL06AnnE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788964767; c=relaxed/simple; bh=5rWyh8R74Dcjd3NQnCi7oo4stmol18OuEwXRpQrVrcs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Jt2a9E9cjj2zkFBw8zyyuY8C8r8DuyeeA8zEbwQTCsxRMB5AHrorKPt2DyFM6Zq/6Hd2LnWxKUbS+KHQvVs+3qiHZn3/VRevVjohcwhLON/+eSSleOFvIcduNWdgIYJRrsUP+oOX/u0KCFFjCiIj4AmMfZdMwr+2gB7Zc4mW2Jc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Y4ndyC9Z; 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="Y4ndyC9Z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86B0C1F00A3D; Wed, 9 Sep 2026 14:39:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788964766; bh=dg3E19PgEP5jU8WjjwDmGDxuLoCFE+DvnHINjY3laiE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Y4ndyC9ZJkz1WCJXBVS+3Zcv0YJrb9O0wEJtEEJr0eIz8gLaustfMN0WCjnxmfIUw 9CjyM15ZT9P1ZU48794k7kO09VA419QahpTJGNlXdn3QUE7gb6keORp9lSjtN5MQSW HG8QKAvP3Utk3FynudIfJiD4397izVs+d2lxCgk4= 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 6.18 536/583] NFSD: Prevent client use-after-free during delegation revoke Date: Wed, 9 Sep 2026 15:43:41 +0200 Message-ID: <20260909134256.350517360@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-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever [ Upstream commit 4683ca76b3b7e5808338491c6eb3c20e6b4894d5 ] A delegation stateid holds only a bare pointer to its owning nfs4_client and does not keep it alive. The client survives its stateids only because __destroy_client() drains cl_delegations and cl_revoked before free_client() runs. nfs4_laundromat() breaks that invariant: it unhashes an expired delegation from cl_delegations, drops deleg_lock, then revoke_delegation() relinks it onto cl_revoked under cl_lock. In that window the delegation is on neither list, so client_has_state() can report no remaining state. Every teardown path first requires cl_rpc_users to be zero, but the laundromat holds no such reference. A client whose recalled delegation has just timed out can therefore reach free_client() while revoke_delegation() is still about to dereference cl_lock, a use-after-free. Pin the client with cl_rpc_users across the revoke so teardown blocks until it completes, then reap the delegation from cl_revoked. A client already expiring reaps its own, so skip it and leave the delegation on del_recall_lru. Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260709-cel-v4-2-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/netns.h | 6 ++++-- fs/nfsd/nfs4state.c | 23 +++++++++++++++++++++++ 2 files changed, 27 insertions(+), 2 deletions(-) --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -102,7 +102,8 @@ struct nfsd_net { struct list_head client_lru; struct list_head close_lru; - /* protects del_recall_lru and delegation hash/unhash */ + /* protects del_recall_lru and delegation hash/unhash; + * nests outside client_lock */ spinlock_t deleg_lock ____cacheline_aligned; struct list_head del_recall_lru; @@ -111,7 +112,8 @@ struct nfsd_net { struct delayed_work laundromat_work; - /* client_lock protects the client lru list and session hash table */ + /* client_lock protects the client lru list and session hash + * table; nests inside deleg_lock */ spinlock_t client_lock; /* protects blocked_locks_lru */ --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7052,6 +7052,7 @@ nfs4_laundromat(struct nfsd_net *nn) .new_timeo = nn->nfsd4_lease }; struct nfs4_cpntf_state *cps; + struct nfs4_client *clp; copy_stateid_t *cps_t; int i; @@ -7080,6 +7081,18 @@ nfs4_laundromat(struct nfsd_net *nn) dp = list_entry (pos, struct nfs4_delegation, dl_recall_lru); if (!state_expired(<, dp->dl_time)) break; + clp = dp->dl_stid.sc_client; + spin_lock(&nn->client_lock); + if (is_client_expired(clp)) { + spin_unlock(&nn->client_lock); + continue; + } + /* + * Pin without reviving: get_client_locked() would + * flip a courtesy client back to NFSD4_ACTIVE. + */ + atomic_inc(&clp->cl_rpc_users); + spin_unlock(&nn->client_lock); refcount_inc(&dp->dl_stid.sc_count); unhash_delegation_locked(dp, SC_STATUS_REVOKED); list_add(&dp->dl_recall_lru, &reaplist); @@ -7088,8 +7101,18 @@ nfs4_laundromat(struct nfsd_net *nn) while (!list_empty(&reaplist)) { dp = list_first_entry(&reaplist, struct nfs4_delegation, dl_recall_lru); + clp = dp->dl_stid.sc_client; list_del_init(&dp->dl_recall_lru); revoke_delegation(dp); + /* + * Unpin without renewing: put_client_renew() would + * renew the reaped client's lease. + */ + if (atomic_dec_and_lock(&clp->cl_rpc_users, &nn->client_lock)) { + if (is_client_expired(clp)) + wake_up_all(&expiry_wq); + spin_unlock(&nn->client_lock); + } } spin_lock(&nn->client_lock);