From: Eric Dumazet <edumazet@google.com>
Date: Wed, 9 Dec 2015 15:25:06 +0000 (-0800)
Subject: ipv6: sctp: clone options to avoid use after free
X-Git-Tag: v4.1.12-92~201^2~13
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=488476113bddac87e2a3e555318dc76f4598a714;p=users%2Fjedix%2Flinux-maple.git

ipv6: sctp: clone options to avoid use after free

Orabug: 22623879

[ Upstream commit 9470e24f35ab81574da54e69df90c1eb4a96b43f ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 683f40ec958e669b0d376a0d83c0213783ee7f99)
Signed-off-by: Dan Duval <dan.duval@oracle.com>
---

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index 0e4198ee2370..3267a5cbb3e8 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -634,6 +634,7 @@ 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);
 	if (!newsk)
@@ -653,6 +654,13 @@ 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().
 	 */