net, sk_msg: Annotate lockless access to sk_prot on clone
sk_msg and ULP frameworks override protocol callbacks pointer in sk->sk_prot, while tcp accesses it locklessly when cloning the listening socket, that is with neither sk_lock nor sk_callback_lock held. Once we enable use of listening sockets with sockmap (and hence sk_msg), there will be shared access to sk->sk_prot if socket is getting cloned while being inserted/deleted to/from the sockmap from another CPU: Read side: tcp_v4_rcv sk = __inet_lookup_skb(...) tcp_check_req(sk) inet_csk(sk)->icsk_af_ops->syn_recv_sock tcp_v4_syn_recv_sock tcp_create_openreq_child inet_csk_clone_lock sk_clone_lock READ_ONCE(sk->sk_prot) Write side: sock_map_ops->map_update_elem sock_map_update_elem sock_map_update_common sock_map_link_no_progs tcp_bpf_init tcp_bpf_update_sk_prot sk_psock_update_proto WRITE_ONCE(sk->sk_prot, ops) sock_map_ops->map_delete_elem sock_map_delete_elem __sock_map_delete sock_map_unref sk_psock_put sk_psock_drop sk_psock_restore_proto tcp_update_ulp WRITE_ONCE(sk->sk_prot, proto) Mark the shared access with READ_ONCE/WRITE_ONCE annotations. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200218171023.844439-2-jakub@cloudflare.com
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@ -352,7 +352,8 @@ static inline void sk_psock_update_proto(struct sock *sk,
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psock->saved_write_space = sk->sk_write_space;
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psock->sk_proto = sk->sk_prot;
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sk->sk_prot = ops;
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/* Pairs with lockless read in sk_clone_lock() */
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WRITE_ONCE(sk->sk_prot, ops);
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}
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static inline void sk_psock_restore_proto(struct sock *sk,
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@ -1572,13 +1572,14 @@ static inline void sock_lock_init(struct sock *sk)
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*/
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static void sock_copy(struct sock *nsk, const struct sock *osk)
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{
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const struct proto *prot = READ_ONCE(osk->sk_prot);
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#ifdef CONFIG_SECURITY_NETWORK
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void *sptr = nsk->sk_security;
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#endif
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memcpy(nsk, osk, offsetof(struct sock, sk_dontcopy_begin));
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memcpy(&nsk->sk_dontcopy_end, &osk->sk_dontcopy_end,
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osk->sk_prot->obj_size - offsetof(struct sock, sk_dontcopy_end));
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prot->obj_size - offsetof(struct sock, sk_dontcopy_end));
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#ifdef CONFIG_SECURITY_NETWORK
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nsk->sk_security = sptr;
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@ -1792,16 +1793,17 @@ static void sk_init_common(struct sock *sk)
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*/
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struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
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{
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struct proto *prot = READ_ONCE(sk->sk_prot);
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struct sock *newsk;
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bool is_charged = true;
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newsk = sk_prot_alloc(sk->sk_prot, priority, sk->sk_family);
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newsk = sk_prot_alloc(prot, priority, sk->sk_family);
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if (newsk != NULL) {
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struct sk_filter *filter;
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sock_copy(newsk, sk);
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newsk->sk_prot_creator = sk->sk_prot;
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newsk->sk_prot_creator = prot;
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/* SANITY */
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if (likely(newsk->sk_net_refcnt))
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@ -645,8 +645,10 @@ static void tcp_bpf_reinit_sk_prot(struct sock *sk, struct sk_psock *psock)
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/* Reinit occurs when program types change e.g. TCP_BPF_TX is removed
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* or added requiring sk_prot hook updates. We keep original saved
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* hooks in this case.
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*
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* Pairs with lockless read in sk_clone_lock().
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*/
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sk->sk_prot = &tcp_bpf_prots[family][config];
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WRITE_ONCE(sk->sk_prot, &tcp_bpf_prots[family][config]);
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}
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static int tcp_bpf_assert_proto_ops(struct proto *ops)
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@ -106,7 +106,8 @@ void tcp_update_ulp(struct sock *sk, struct proto *proto,
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if (!icsk->icsk_ulp_ops) {
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sk->sk_write_space = write_space;
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sk->sk_prot = proto;
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/* Pairs with lockless read in sk_clone_lock() */
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WRITE_ONCE(sk->sk_prot, proto);
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return;
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}
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@ -742,7 +742,8 @@ static void tls_update(struct sock *sk, struct proto *p,
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ctx->sk_write_space = write_space;
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ctx->sk_proto = p;
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} else {
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sk->sk_prot = p;
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/* Pairs with lockless read in sk_clone_lock(). */
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WRITE_ONCE(sk->sk_prot, p);
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sk->sk_write_space = write_space;
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}
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}
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