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net: bpf: Handle return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND()

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The return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND() in
__inet_bind() is not handled properly. While the return value
is non-zero, it will set inet_saddr and inet_rcv_saddr to 0 and
exit:

	err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
	if (err) {
		inet->inet_saddr = inet->inet_rcv_saddr = 0;
		goto out_release_sock;
	}

Let's take UDP for example and see what will happen. For UDP
socket, it will be added to 'udp_prot.h.udp_table->hash' and
'udp_prot.h.udp_table->hash2' after the sk->sk_prot->get_port()
called success. If 'inet->inet_rcv_saddr' is specified here,
then 'sk' will be in the 'hslot2' of 'hash2' that it don't belong
to (because inet_saddr is changed to 0), and UDP packet received
will not be passed to this sock. If 'inet->inet_rcv_saddr' is not
specified here, the sock will work fine, as it can receive packet
properly, which is wired, as the 'bind()' is already failed.

To undo the get_port() operation, introduce the 'put_port' field
for 'struct proto'. For TCP proto, it is inet_put_port(); For UDP
proto, it is udp_lib_unhash(); For icmp proto, it is
ping_unhash().

Therefore, after sys_bind() fail caused by
BPF_CGROUP_RUN_PROG_INET4_POST_BIND(), it will be unbinded, which
means that it can try to be binded to another port.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220106132022.3470772-2-imagedong@tencent.com
This commit is contained in:
Menglong Dong 2022-01-06 21:20:20 +08:00 committed by Alexei Starovoitov
parent 44bab87d8c
commit 91a760b269
9 changed files with 11 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/sock.h
View File

@ -1209,6 +1209,7 @@ struct proto {
void (*unhash)(struct sock *sk);
void (*rehash)(struct sock *sk);
int (*get_port)(struct sock *sk, unsigned short snum);
void (*put_port)(struct sock *sk);
#ifdef CONFIG_BPF_SYSCALL
int (*psock_update_sk_prot)(struct sock *sk,
struct sk_psock *psock,

2
net/ipv4/af_inet.c
View File

@ -531,6 +531,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
if (err) {
inet->inet_saddr = inet->inet_rcv_saddr = 0;
if (sk->sk_prot->put_port)
sk->sk_prot->put_port(sk);
goto out_release_sock;
}
}

1
net/ipv4/ping.c
View File

@ -994,6 +994,7 @@ struct proto ping_prot = {
.hash = ping_hash,
.unhash = ping_unhash,
.get_port = ping_get_port,
.put_port = ping_unhash,
.obj_size = sizeof(struct inet_sock),
};
EXPORT_SYMBOL(ping_prot);

1
net/ipv4/tcp_ipv4.c
View File

@ -3076,6 +3076,7 @@ struct proto tcp_prot = {
.hash = inet_hash,
.unhash = inet_unhash,
.get_port = inet_csk_get_port,
.put_port = inet_put_port,
#ifdef CONFIG_BPF_SYSCALL
.psock_update_sk_prot = tcp_bpf_update_proto,
#endif

1
net/ipv4/udp.c
View File

@ -2927,6 +2927,7 @@ struct proto udp_prot = {
.unhash = udp_lib_unhash,
.rehash = udp_v4_rehash,
.get_port = udp_v4_get_port,
.put_port = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
.psock_update_sk_prot = udp_bpf_update_proto,
#endif

2
net/ipv6/af_inet6.c
View File

@ -413,6 +413,8 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
if (err) {
sk->sk_ipv6only = saved_ipv6only;
inet_reset_saddr(sk);
if (sk->sk_prot->put_port)
sk->sk_prot->put_port(sk);
goto out;
}
}

1
net/ipv6/ping.c
View File

@ -177,6 +177,7 @@ struct proto pingv6_prot = {
.hash = ping_hash,
.unhash = ping_unhash,
.get_port = ping_get_port,
.put_port = ping_unhash,
.obj_size = sizeof(struct raw6_sock),
};
EXPORT_SYMBOL_GPL(pingv6_prot);

1
net/ipv6/tcp_ipv6.c
View File

@ -2181,6 +2181,7 @@ struct proto tcpv6_prot = {
.hash = inet6_hash,
.unhash = inet_unhash,
.get_port = inet_csk_get_port,
.put_port = inet_put_port,
#ifdef CONFIG_BPF_SYSCALL
.psock_update_sk_prot = tcp_bpf_update_proto,
#endif

1
net/ipv6/udp.c
View File

@ -1732,6 +1732,7 @@ struct proto udpv6_prot = {
.unhash = udp_lib_unhash,
.rehash = udp_v6_rehash,
.get_port = udp_v6_get_port,
.put_port = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
.psock_update_sk_prot = udp_bpf_update_proto,
#endif