@@ -413,6 +413,20 @@ static void subflow_ulp_fallback(struct sock *sk,
tcp_sk(sk)->is_mptcp = 0;
}
+static void subflow_drop_ctx(struct sock *ssk)
+{
+ struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
+
+ if (!ctx)
+ return;
+
+ subflow_ulp_fallback(ssk, ctx);
+ if (ctx->conn)
+ sock_put(ctx->conn);
+
+ kfree_rcu(ctx, rcu);
+}
+
static struct sock *subflow_syn_recv_sock(const struct sock *sk,
struct sk_buff *skb,
struct request_sock *req,
@@ -485,10 +499,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
if (fallback_is_fatal)
goto dispose_child;
- if (ctx) {
- subflow_ulp_fallback(child, ctx);
- kfree_rcu(ctx, rcu);
- }
+ subflow_drop_ctx(child);
goto out;
}
@@ -537,6 +548,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
return child;
dispose_child:
+ subflow_drop_ctx(child);
tcp_rsk(req)->drop_req = true;
tcp_send_active_reset(child, GFP_ATOMIC);
inet_csk_prepare_for_destroy_sock(child);
When token lookup on MP_JOIN 3rd ack fails, the server socket closes with a reset the incoming child. Such socket has the 'is_mptcp' flag set, but no msk socket associated - due to the failed lookup. While crafting the reset packet mptcp_established_options_mp() will try to dereference the child's master socket, causing a NULL ptr dereference. This change addresses the issue with explicit fallback to TCP in such error path. Fixes: 729cd6436f35 ("mptcp: cope better with MP_JOIN failure") Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/subflow.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)