net/smc: Fix af_ops of child socket pointing to released memory

karstengr · kuba-moo · commit 49b7d376abe5 · 2022-04-11T18:28:03.000-07:00
Child sockets may inherit the af_ops from the parent listen socket. When the listen socket is released then the af_ops of the child socket points to released memory. Solve that by restoring the original af_ops for child sockets which inherited the parent af_ops. And clear any inherited user_data of the parent socket. Fixes: 8270d9c ("net/smc: Limit backlog connections") Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com> Signed-off-by: Karsten Graul <kgraul@linux.ibm.com> Reviewed-by: D. Wythe <alibuda@linux.alibaba.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
@@ -121,6 +121,7 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
 					  bool *own_req)
 {
 	struct smc_sock *smc;
+	struct sock *child;
 
 	smc = smc_clcsock_user_data(sk);
 
@@ -134,8 +135,17 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk,
 	}
 
 	/* passthrough to original syn recv sock fct */
-	return smc->ori_af_ops->syn_recv_sock(sk, skb, req, dst, req_unhash,
-					      own_req);
+	child = smc->ori_af_ops->syn_recv_sock(sk, skb, req, dst, req_unhash,
+					       own_req);
+	/* child must not inherit smc or its ops */
+	if (child) {
+		rcu_assign_sk_user_data(child, NULL);
+
+		/* v4-mapped sockets don't inherit parent ops. Don't restore. */
+		if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops)
+			inet_csk(child)->icsk_af_ops = smc->ori_af_ops;
+	}
+	return child;
 
 drop:
 	dst_release(dst);
