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Subject[PATCH net] ipv6: sctp: clone options to avoid use after free
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Date
From: Eric Dumazet <edumazet@google.com>

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>
---
net/sctp/ipv6.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index d28c0b4c9128..ec529121f38a 100644
--- 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().
*/



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