From 20b5759f21cf53a0e03031bd3fe539e332b13568 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Tue, 25 May 2021 14:23:10 -0700 Subject: [PATCH] mptcp: avoid OOB access in setsockopt() We can't use tcp_set_congestion_control() on an mptcp socket, as such function can end-up accessing a tcp-specific field - prior_ssthresh - causing an OOB access. To allow propagating the correct ca algo on subflow, cache the ca name at initialization time. Additionally avoid overriding the user-selected CA (if any) at clone time. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/182 Fixes: aa1fbd94e5c7 ("mptcp: sockopt: add TCP_CONGESTION and TCP_INFO") Acked-by: Florian Westphal Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/protocol.c | 14 +++++++++++--- net/mptcp/protocol.h | 1 + net/mptcp/sockopt.c | 4 ++-- 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 2d21a47..2bc1995 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2424,13 +2424,12 @@ static int __mptcp_init_sock(struct sock *sk) timer_setup(&msk->sk.icsk_retransmit_timer, mptcp_retransmit_timer, 0); timer_setup(&sk->sk_timer, mptcp_timeout_timer, 0); - tcp_assign_congestion_control(sk); - return 0; } static int mptcp_init_sock(struct sock *sk) { + struct inet_connection_sock *icsk = inet_csk(sk); struct net *net = sock_net(sk); int ret; @@ -2448,6 +2447,16 @@ static int mptcp_init_sock(struct sock *sk) if (ret) return ret; + /* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will + * propagate the correct value + */ + tcp_assign_congestion_control(sk); + strcpy(mptcp_sk(sk)->ca_name, icsk->icsk_ca_ops->name); + + /* no need to keep a reference to the ops, the name will suffice */ + tcp_cleanup_congestion_control(sk); + icsk->icsk_ca_ops = NULL; + sk_sockets_allocated_inc(sk); sk->sk_rcvbuf = sock_net(sk)->ipv4.sysctl_tcp_rmem[1]; sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[1]; @@ -2622,7 +2631,6 @@ static void __mptcp_destroy_sock(struct sock *sk) sk_stream_kill_queues(sk); xfrm_sk_free_policy(sk); - tcp_cleanup_congestion_control(sk); sk_refcnt_debug_release(sk); mptcp_dispose_initial_subflow(msk); sock_put(sk); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index edc0128..165c8b4 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -258,6 +258,7 @@ struct mptcp_sock { } rcvq_space; u32 setsockopt_seq; + char ca_name[TCP_CA_NAME_MAX]; }; #define mptcp_lock_sock(___sk, cb) do { \ diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index 00d941b..a797981 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -547,7 +547,7 @@ static int mptcp_setsockopt_sol_tcp_congestion(struct mptcp_sock *msk, sockptr_t } if (ret == 0) - tcp_set_congestion_control(sk, name, false, cap_net_admin); + strcpy(msk->ca_name, name); release_sock(sk); return ret; @@ -705,7 +705,7 @@ static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk) sock_valbool_flag(ssk, SOCK_DBG, sock_flag(sk, SOCK_DBG)); if (inet_csk(sk)->icsk_ca_ops != inet_csk(ssk)->icsk_ca_ops) - tcp_set_congestion_control(ssk, inet_csk(sk)->icsk_ca_ops->name, false, true); + tcp_set_congestion_control(ssk, msk->ca_name, false, true); } static void __mptcp_sockopt_sync(struct mptcp_sock *msk, struct sock *ssk) -- 2.7.4