New sockets cloned from listening sockets that are in a sockmap must not
inherit the psock that has the link to the sockmap. Otherwise child sockets
unintentionally share the sockmap entry with the listening socket, which
leads to double-free on socket close.
Prevent it by overloading the accept callback. In it we restore the
protocol and write buffer callbacks and clear the pointer to psock.
Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
---
net/ipv4/tcp_bpf.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 8a56e09cfb0e..5838aaba4ce0 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -582,6 +582,35 @@ static void tcp_bpf_close(struct sock *sk, long timeout)
saved_close(sk, timeout);
}
+static struct sock *tcp_bpf_accept(struct sock *sk, int flags, int *err,
+ bool kern)
+{
+ void (*saved_write_space)(struct sock *sk);
+ struct proto *saved_proto;
+ struct sk_psock *psock;
+ struct sock *child;
+
+ rcu_read_lock();
+ psock = sk_psock(sk);
+ if (unlikely(!psock)) {
+ rcu_read_unlock();
+ return sk->sk_prot->accept(sk, flags, err, kern);
+ }
+ saved_proto = psock->sk_proto;
+ saved_write_space = psock->saved_write_space;
+ rcu_read_unlock();
+
+ child = saved_proto->accept(sk, flags, err, kern);
+ if (!child)
+ return NULL;
+
+ /* Child must not inherit psock or its ops. */
+ rcu_assign_sk_user_data(child, NULL);
+ child->sk_prot = saved_proto;
+ child->sk_write_space = saved_write_space;
+ return child;
+}
+
enum {
TCP_BPF_IPV4,
TCP_BPF_IPV6,
@@ -606,6 +635,7 @@ static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
prot[TCP_BPF_BASE].close = tcp_bpf_close;
prot[TCP_BPF_BASE].recvmsg = tcp_bpf_recvmsg;
prot[TCP_BPF_BASE].stream_memory_read = tcp_bpf_stream_read;
+ prot[TCP_BPF_BASE].accept = tcp_bpf_accept;
prot[TCP_BPF_TX] = prot[TCP_BPF_BASE];
prot[TCP_BPF_TX].sendmsg = tcp_bpf_sendmsg;
--
2.20.1
