Commit 20b5759f authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

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.

Fixes: aa1fbd94

 ("mptcp: sockopt: add TCP_CONGESTION and TCP_INFO")
Acked-by: default avatarFlorian Westphal <>
Signed-off-by: default avatarPaolo Abeni <>
Signed-off-by: default avatarMat Martineau <>
Signed-off-by: default avatarDavid S. Miller <>
parent bab09fe2
......@@ -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);
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
strcpy(mptcp_sk(sk)->ca_name, icsk->icsk_ca_ops->name);
/* no need to keep a reference to the ops, the name will suffice */
icsk->icsk_ca_ops = NULL;
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)
......@@ -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 { \
......@@ -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);
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)
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