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

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

diff --git a/include/net/sock.h b/include/net/sock.h
index 7b4b4237e6e0fb0e914e7a50e5c1f2967c399750..ff9b508d9c5ffcb9a30deb730b27046e463bda37 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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,

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index f53184767ee727b3ea16415849b171fb7e0552b5..9c465bac1eb0e4e43c5fdc749e27751c34206f73 100644 (file)
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -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;
                        }
                }

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index e540b0dcf08549316f7585a1929ef1323175d282..0e56df3a45e266771b7bb02e3ce7a920d2b19d29 100644 (file)
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -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);

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ac10e4cdd8d0ae006a32ace257dedf4084803db1..9861786b8336533bd926a81c89593d7ab41270d7 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -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

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 7b18a6f42f18f3693bdf2eb12519656c749cbc88..c2a4411d2b04dd475c359ea18f57c59fee6b0f88 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -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

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index d1636425654e28140862be4095925953f56eaae8..8fe7900f1949911b32326fb166ae20912a59c215 100644 (file)
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -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;
                        }
                }

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index 6ac88fe24a8e076e59c706413e2241fcf0288260..9256f6ba87ef4e22183658e32a0a2dd637df5ee5 100644 (file)
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c
@@ -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);

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1ac243d18c2b446b94332470e0c3dcc5caeab2ee..075ee8a2df3b7f3759f69f1b1256f2e8c9c700c1 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -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

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 1accc06abc542866270cc3524d5396efdef7ad69..90718a924ca82e5aefc09a2f215a80bdedcfe88f 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -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