From b8e202d1d1d0f182f01062804efb523ea9a9008c Mon Sep 17 00:00:00 2001 From: Jakub Sitnicki Date: Tue, 18 Feb 2020 17:10:13 +0000 Subject: 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 Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200218171023.844439-2-jakub@cloudflare.com --- net/ipv4/tcp_bpf.c | 4 +++- net/ipv4/tcp_ulp.c | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 8a01428f80c1..dd183b050642 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -645,8 +645,10 @@ static void tcp_bpf_reinit_sk_prot(struct sock *sk, struct sk_psock *psock) /* Reinit occurs when program types change e.g. TCP_BPF_TX is removed * or added requiring sk_prot hook updates. We keep original saved * hooks in this case. + * + * Pairs with lockless read in sk_clone_lock(). */ - sk->sk_prot = &tcp_bpf_prots[family][config]; + WRITE_ONCE(sk->sk_prot, &tcp_bpf_prots[family][config]); } static int tcp_bpf_assert_proto_ops(struct proto *ops) diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c index 38d3ad141161..6c43fa189195 100644 --- a/net/ipv4/tcp_ulp.c +++ b/net/ipv4/tcp_ulp.c @@ -106,7 +106,8 @@ void tcp_update_ulp(struct sock *sk, struct proto *proto, if (!icsk->icsk_ulp_ops) { sk->sk_write_space = write_space; - sk->sk_prot = proto; + /* Pairs with lockless read in sk_clone_lock() */ + WRITE_ONCE(sk->sk_prot, proto); return; } -- cgit v1.2.3