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skmsg: Update saved hooks only once 

Only update psock->saved_* if psock->sk_proto has not been initialized
yet. This allows us to get rid of tcp_bpf_reinit_sk_prot.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200309111243.6982-3-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer 2020-03-09 11:12:33 +00:00 committed by Daniel Borkmann
parent 7b70973d7e
commit 1a2e20132d
2 changed files with 17 additions and 19 deletions
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20
include/linux/skmsg.h
View File

@ -347,11 +347,23 @@ static inline void sk_psock_update_proto(struct sock *sk,
struct sk_psock *psock,
struct proto *ops)
{
psock->saved_unhash = sk->sk_prot->unhash;
psock->saved_close = sk->sk_prot->close;
psock->saved_write_space = sk->sk_write_space;
/* Initialize saved callbacks and original proto only once, since this
* function may be called multiple times for a psock, e.g. when
* psock->progs.msg_parser is updated.
*
* Since we've not installed the new proto, psock is not yet in use and
* we can initialize it without synchronization.
*/
if (!psock->sk_proto) {
struct proto *orig = READ_ONCE(sk->sk_prot);
psock->saved_unhash = orig->unhash;
psock->saved_close = orig->close;
psock->saved_write_space = sk->sk_write_space;
psock->sk_proto = orig;
}
psock->sk_proto = sk->sk_prot;
/* Pairs with lockless read in sk_clone_lock() */
WRITE_ONCE(sk->sk_prot, ops);
}

16
net/ipv4/tcp_bpf.c
View File

@ -637,20 +637,6 @@ static void tcp_bpf_update_sk_prot(struct sock *sk, struct sk_psock *psock)
sk_psock_update_proto(sk, psock, &tcp_bpf_prots[family][config]);
}
static void tcp_bpf_reinit_sk_prot(struct sock *sk, struct sk_psock *psock)
{
int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
int config = psock->progs.msg_parser ? TCP_BPF_TX : TCP_BPF_BASE;
/* 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().
*/
WRITE_ONCE(sk->sk_prot, &tcp_bpf_prots[family][config]);
}
static int tcp_bpf_assert_proto_ops(struct proto *ops)
{
/* In order to avoid retpoline, we make assumptions when we call
@ -670,7 +656,7 @@ void tcp_bpf_reinit(struct sock *sk)
rcu_read_lock();
psock = sk_psock(sk);
tcp_bpf_reinit_sk_prot(sk, psock);
tcp_bpf_update_sk_prot(sk, psock);
rcu_read_unlock();
}