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

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: b21c61a713ac ("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
index f0d118e9f155178e80f78d3e16d36126873d16dd..14ddc40149e8f0bd555a075f1914b8b422867f79 100644 (file)
--- 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);