mptcp: fix splat when incoming connection is never accepted before exit/close (df1036da) · Commits · 戴 / test

Following snippet (replicated from syzkaller reproducer) generates warning: "IPv4: Attempt to release TCP socket in state 1". int main(void) { struct sockaddr_in sin1 = { .sin_family = 2, .sin_port = 0x4e20, .sin_addr.s_addr = 0x010000e0, }; struct sockaddr_in sin2 = { .sin_family = 2, .sin_addr.s_addr = 0x0100007f, }; struct sockaddr_in sin3 = { .sin_family = 2, .sin_port = 0x4e20, .sin_addr.s_addr = 0x0100007f, }; int r0 = socket(0x2, 0x1, 0x106); int r1 = socket(0x2, 0x1, 0x106); bind(r1, (void *)&sin1, sizeof(sin1)); connect(r1, (void *)&sin2, sizeof(sin2)); listen(r1, 3); return connect(r0, (void *)&sin3, 0x4d); } Reason is that the newly generated mptcp socket is closed via the ulp release of the tcp listener socket when its accept backlog gets purged. To fix this, delay setting the ESTABLISHED state until after userspace calls accept and via mptcp specific destructor. Fixes: ("mptcp: create msk early") Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/9 Signed-off-by:

Florian Westphal <fw@strlen.de> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1431,6 +1431,7 @@ static struct sock mptcp_accept(struct sock sk, int flags, int *err,
		newsk = new_mptcp_sock;
		mptcp_copy_inaddrs(newsk, ssk);
		list_add(&subflow->node, &msk->conn_list);
		inet_sk_state_store(newsk, TCP_ESTABLISHED);

		bh_unlock_sock(new_mptcp_sock);

net/mptcp/subflow.c

+24 −1

Original line number	Diff line number	Diff line
		@@ -347,6 +347,29 @@ static bool subflow_hmac_valid(const struct request_sock *req,
		return ret;
		}

		static void mptcp_sock_destruct(struct sock *sk)
		{
		/* if new mptcp socket isn't accepted, it is free'd
		* from the tcp listener sockets request queue, linked
		* from req->sk. The tcp socket is released.
		* This calls the ULP release function which will
		* also remove the mptcp socket, via
		* sock_put(ctx->conn).
		*
		* Problem is that the mptcp socket will not be in
		* SYN_RECV state and doesn't have SOCK_DEAD flag.
		* Both result in warnings from inet_sock_destruct.
		*/

		if (sk->sk_state == TCP_SYN_RECV) {
		sk->sk_state = TCP_CLOSE;
		WARN_ON_ONCE(sk->sk_socket);
		sock_orphan(sk);
		}

		inet_sock_destruct(sk);
		}

		static struct sock subflow_syn_recv_sock(const struct sock sk,
		struct sk_buff *skb,
		struct request_sock *req,
		@@ -422,7 +445,7 @@ create_child:
		/* new mpc subflow takes ownership of the newly
		* created mptcp socket
		*/
		inet_sk_state_store(new_msk, TCP_ESTABLISHED);
		new_msk->sk_destruct = mptcp_sock_destruct;
		mptcp_pm_new_connection(mptcp_sk(new_msk), 1);
		ctx->conn = new_msk;
		new_msk = NULL;

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