ipv6: sctp: clone options to avoid use after free

SCTP is lacking proper np->opt cloning at accept() time.

TCP and DCCP use ipv6_dup_options() helper, do the same
in SCTP.

We might later factorize this code in a common helper to avoid
future mistakes.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index d28c0b4c9128949bcd193a815ef6ed2c705fe677..ec529121f38a03c4b3e2317249cd0694fd619d3f 100644 (file)
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -641,6 +641,7 @@ static struct sock *sctp_v6_create_accept_sk(struct sock *sk,
        struct sock *newsk;
        struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
        struct sctp6_sock *newsctp6sk;
+       struct ipv6_txoptions *opt;
 
        newsk = sk_alloc(sock_net(sk), PF_INET6, GFP_KERNEL, sk->sk_prot, 0);
        if (!newsk)
@@ -660,6 +661,13 @@ static struct sock *sctp_v6_create_accept_sk(struct sock *sk,
 
        memcpy(newnp, np, sizeof(struct ipv6_pinfo));
 
+       rcu_read_lock();
+       opt = rcu_dereference(np->opt);
+       if (opt)
+               opt = ipv6_dup_options(newsk, opt);
+       RCU_INIT_POINTER(newnp->opt, opt);
+       rcu_read_unlock();
+
        /* Initialize sk's sport, dport, rcv_saddr and daddr for getsockname()
         * and getpeername().
         */