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tcp_bpf: Don't let child socket inherit parent protocol ops on copy

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Prepare for cloning listening sockets that have their protocol callbacks
overridden by sk_msg. Child sockets must not inherit parent callbacks that
access state stored in sk_user_data owned by the parent.

Restore the child socket protocol callbacks before it gets hashed and any
of the callbacks can get invoked.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200218171023.844439-4-jakub@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2020-02-18 17:10:15 +00:00 committed by Daniel Borkmann
parent f1ff5ce2cd
commit e80251555f
3 changed files with 23 additions and 0 deletions
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7
include/net/tcp.h
View File

@ -2203,6 +2203,13 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
int nonblock, int flags, int *addr_len);
int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
struct msghdr *msg, int len, int flags);
#ifdef CONFIG_NET_SOCK_MSG
void tcp_bpf_clone(const struct sock *sk, struct sock *newsk);
#else
static inline void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
{
}
#endif
/* Call BPF_SOCK_OPS program that returns an int. If the return value
* is < 0, then the BPF op failed (for example if the loaded BPF

14
net/ipv4/tcp_bpf.c
View File

@ -693,3 +693,17 @@ int tcp_bpf_init(struct sock *sk)
rcu_read_unlock();
return 0;
}
/* If a child got cloned from a listening socket that had tcp_bpf
* protocol callbacks installed, we need to restore the callbacks to
* the default ones because the child does not inherit the psock state
* that tcp_bpf callbacks expect.
*/
void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
{
int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
struct proto *prot = newsk->sk_prot;
if (prot == &tcp_bpf_prots[family][TCP_BPF_BASE])
newsk->sk_prot = sk->sk_prot_creator;
}

2
net/ipv4/tcp_minisocks.c
View File

@ -548,6 +548,8 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
newtp->fastopen_req = NULL;
RCU_INIT_POINTER(newtp->fastopen_rsk, NULL);
tcp_bpf_clone(sk, newsk);
__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);
return newsk;