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 52CD835E549; Mon, 14 Sep 2026 03:37:26 +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=1789357048; cv=none; b=mt7sfZks0sbv3f1iH4M9GN6LanMolJEQykwnBfTys9G8ugyeo0Rf+56Q72VQpDZjcyJ7lDxE1P0O8RT7qsaerTuivPkK1PDONtqspzJ0pfKYV4cgXFOxl4Y09y5kEZMDSoh/Al1N0CDirAD261D/RYTA4cg10LVPM8FALzEsdmA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789357048; c=relaxed/simple; bh=Hsrb4gMW0rL5A7AQ5jknzAFAplkHC1fmovyqJ+LcJHE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=FvFiZlEVX4o1J4c3OwiO12WJ5wNiQk/N1owsyCVOvZ0bnhVR3R8SzMh8lxwH2cQd/kayczvX48DR1J4dJSg+oJn1Q9b4Jj366m/e3LwjRzUqsYdoItX0hmpZ0t9ResE9MQWh3ri1ANCVpHCIMqpqgKVZy2oz15Vf1jiXOtQZ+Fk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ju2+fXun; 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="ju2+fXun" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6B371F0089B; Mon, 14 Sep 2026 03:37:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789357046; bh=/Y41WzDVHzLsdmaFRSRgp0HF2V4Wh7LJpKGkzWoTBCU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ju2+fXunr8b0F6lWb/GNQDnvHWPP7AEX0/tMEnj16KiFRKyKWlt4LJBQoe2lz9WRj MCbHsML8EJdXRUn0fZ1hUhFPLJQqwbYjgKhKWfZoYI/aJXdb38K8K8TAqhEZyUig1k ZQdMzyNbyftanTOGfrkQWL5SXgCU/eHFHdo1BrJBVMAOqIHkCdttJM8+GYkWl4tjIk v0PLl9ZSx38GbIdA9xsprgE2d49BehkMfAIAgK20akA4iMczYvxhnlpBzw1jLAuMyW oaTYs66ViGlobadxPT5ewHYsvYwCDQRh8BAsplSBkZZik8KogErOXa4NtCEKd1an99 R1IZwETR1YRPw== From: Allison Henderson To: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, kuba@kernel.org, horms@kernel.org Cc: achender@kernel.org, nicoyip.dev@gmail.com Subject: [PATCH net-next v3 11/13] net/rds: pin the connection across RDMA-CM event handling Date: Sun, 13 Sep 2026 20:37:17 -0700 Message-Id: <20260914033719.138057-12-achender@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260914033719.138057-1-achender@kernel.org> References: <20260914033719.138057-1-achender@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rds_rdma_cm_event_handler_cmn() picks the connection up from cm_id->context, which carries no reference, and holds c_cm_lock - a mutex that lives in the connection's path array - across the transport callbacks. Now that a connection is freed by its last reference rather than by rds_conn_destroy() itself, a callback that drops the last reference other than the handler's implicit one leaves the final mutex_unlock() running on freed memory. Take a reference for the duration of the handler, and ignore the event if the connection is already being freed: its cm_id teardown is what stops event delivery, so an event that still arrives belongs to a connection whose shutdown has run and whose memory is on its way out. rds_ib_cm_handle_connect() has the mirror-image hole: a connection whose destroy has already quiesced it sits in RDS_CONN_DOWN with no cm_id, which is exactly the state the DOWN -> CONNECTING transition claims. A connect request arriving then would install a new cm_id and QP on a connection that is only waiting for its last reference to go away, and nothing would tear them down again. Re-check rds_destroy_pending() under c_cm_lock and reject the request instead. Assisted-by: Claude-Code:claude-fable-5 Signed-off-by: Allison Henderson --- net/rds/ib_cm.c | 7 +++++++ net/rds/rdma_transport.c | 16 +++++++++++++++- net/rds/rds.h | 5 +++++ 3 files changed, 27 insertions(+), 1 deletion(-) diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c index 5a4644c40be5..257e03ed4861 100644 --- a/net/rds/ib_cm.c +++ b/net/rds/ib_cm.c @@ -874,6 +874,13 @@ int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id, * see the comment above rds_queue_reconnect() */ mutex_lock(&conn->c_cm_lock); + /* A destroy that has already quiesced this conn leaves it in + * RDS_CONN_DOWN with no cm_id, exactly what the transition + * below would happily claim; nothing would tear the new cm_id + * and QP down again before the conn is freed. Reject instead. + */ + if (rds_destroy_pending(conn)) + goto out; if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) { if (rds_conn_state(conn) == RDS_CONN_UP) { rdsdebug("incoming connect while connecting\n"); diff --git a/net/rds/rdma_transport.c b/net/rds/rdma_transport.c index b15cf316b23a..584e9867810f 100644 --- a/net/rds/rdma_transport.c +++ b/net/rds/rdma_transport.c @@ -63,6 +63,18 @@ static int rds_rdma_cm_event_handler_cmn(struct rdma_cm_id *cm_id, if (cm_id->device->node_type == RDMA_NODE_IB_CA) trans = &rds_ib_transport; + /* cm_id->context carries no reference of its own. Pin the + * connection for the duration of the handler: what the callbacks + * below do may drop the last reference other than ours, and the + * mutex released at out: lives in the connection's path array. + * A connection already being freed gets no events handled. + */ + if (conn && !rds_conn_get_unless_zero(conn)) { + rdsdebug("conn %p id %p is being freed, ignoring event\n", + conn, cm_id); + return 0; + } + /* Prevent shutdown from tearing down the connection * while we're executing. */ if (conn) { @@ -171,8 +183,10 @@ static int rds_rdma_cm_event_handler_cmn(struct rdma_cm_id *cm_id, } out: - if (conn) + if (conn) { mutex_unlock(&conn->c_cm_lock); + rds_conn_put(conn); + } rdsdebug("id %p event %u (%s) handling ret %d\n", cm_id, event->event, rdma_event_msg(event->event), ret); diff --git a/net/rds/rds.h b/net/rds/rds.h index 4608615e09e9..06d48c2821ef 100644 --- a/net/rds/rds.h +++ b/net/rds/rds.h @@ -840,6 +840,11 @@ void rds_conn_shutdown(struct rds_conn_path *cpath); void rds_conn_destroy(struct rds_connection *conn); void rds_conn_get(struct rds_connection *conn); void rds_conn_put(struct rds_connection *conn); +/* take a reference unless the connection is already being freed */ +static inline bool rds_conn_get_unless_zero(struct rds_connection *conn) +{ + return kref_get_unless_zero(&conn->c_refcount); +} /* transport unload waits for its connections to be freed, polling at * the first interval and warning at the second */ -- 2.25.1