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| author | Jakub Sitnicki <jakub@cloudflare.com> | 2020-02-18 17:10:13 +0000 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-02-21 22:29:45 +0100 |
| commit | b8e202d1d1d0f182f01062804efb523ea9a9008c (patch) | |
| tree | 57a1c1d075e2d470fd9c1487744286c2f3bed747 /include/linux/skmsg.h | |
| parent | e42da4c62abb547d9c9138e0e7fcd1f36057b5e8 (diff) | |
| download | lwn-b8e202d1d1d0f182f01062804efb523ea9a9008c.tar.gz lwn-b8e202d1d1d0f182f01062804efb523ea9a9008c.zip | |
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
Diffstat (limited to 'include/linux/skmsg.h')
| -rw-r--r-- | include/linux/skmsg.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h index d90ef61712a1..112765bd146d 100644 --- a/include/linux/skmsg.h +++ b/include/linux/skmsg.h @@ -352,7 +352,8 @@ static inline void sk_psock_update_proto(struct sock *sk, psock->saved_write_space = sk->sk_write_space; psock->sk_proto = sk->sk_prot; - sk->sk_prot = ops; + /* Pairs with lockless read in sk_clone_lock() */ + WRITE_ONCE(sk->sk_prot, ops); } static inline void sk_psock_restore_proto(struct sock *sk, |