From: Jakub Sitnicki <jakub@cloudflare.com>
To: bpf@vger.kernel.org
Cc: John Fastabend <john.fastabend@gmail.com>,
Martin KaFai Lau <kafai@fb.com>,
netdev@vger.kernel.org, kernel-team@cloudflare.com
Subject: [RFC bpf-next 3/5] bpf, sockmap: Don't let child socket inherit psock or its ops on copy
Date: Tue, 22 Oct 2019 13:37:28 +0200 [thread overview]
Message-ID: <20191022113730.29303-4-jakub@cloudflare.com> (raw)
In-Reply-To: <20191022113730.29303-1-jakub@cloudflare.com>
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@cloudflare.com>
---
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
next prev parent reply other threads:[~2019-10-22 11:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 11:37 [RFC bpf-next 0/5] Extend SOCKMAP to store listening sockets Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 1/5] bpf, sockmap: Let BPF helpers use lookup operation on SOCKMAP Jakub Sitnicki
2019-10-24 16:59 ` John Fastabend
2019-10-22 11:37 ` [RFC bpf-next 2/5] bpf, sockmap: Allow inserting listening TCP sockets into SOCKMAP Jakub Sitnicki
2019-10-24 17:06 ` John Fastabend
2019-10-25 9:41 ` Jakub Sitnicki
2019-10-22 11:37 ` Jakub Sitnicki [this message]
2019-10-22 11:37 ` [RFC bpf-next 4/5] bpf: Allow selecting reuseport socket from a SOCKMAP Jakub Sitnicki
2019-10-22 11:37 ` [RFC bpf-next 5/5] selftests/bpf: Extend SK_REUSEPORT tests to cover SOCKMAP Jakub Sitnicki
2019-10-24 16:12 ` [RFC bpf-next 0/5] Extend SOCKMAP to store listening sockets Alexei Starovoitov
2019-10-24 16:56 ` John Fastabend
2019-10-25 9:26 ` Jakub Sitnicki
2019-10-25 14:18 ` John Fastabend
2019-10-28 5:52 ` Martin Lau
2019-10-28 12:35 ` Jakub Sitnicki
2019-10-28 19:04 ` John Fastabend
2019-10-29 8:56 ` Jakub Sitnicki
2019-10-28 20:42 ` Martin Lau
2019-10-28 21:05 ` John Fastabend
2019-10-28 21:38 ` Martin Lau
2019-10-29 8:52 ` Jakub Sitnicki
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