From:   menglong8.dong@gmail.com
To:     kuba@kernel.org, edumazet@google.com
Cc:     davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org,
        shuah@kernel.org, ast@kernel.org, daniel@iogearbox.net,
        andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
        john.fastabend@gmail.com, kpsingh@kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, bpf@vger.kernel.org,
        Menglong Dong <imagedong@tencent.com>
Subject: [PATCH v4 net-next 0/3] net: bpf: handle return value of post_bind{4,6} and add selftests for it
Date:   Thu,  6 Jan 2022 09:57:18 +0800
Message-Id: <20220106015721.3038819-1-imagedong@tencent.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Menglong Dong <imagedong@tencent.com>

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:
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.

The second patch is the selftests for this modification.

The third patch use C99 initializers in test_sock.c.

Changes since v3:
- add the third patch which use C99 initializers in test_sock.c

Changes since v2:
- NULL check for sk->sk_prot->put_port

Changes since v1:
- introduce 'put_port' field for 'struct proto'
- add selftests for it


Menglong Dong (3):
  net: bpf: handle return value of 
    BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND()
  bpf: selftests: add bind retry for post_bind{4, 6}
  bpf: selftests: use C99 initializers in test_sock.c

 include/net/sock.h                      |   1 +
 net/ipv4/af_inet.c                      |   2 +
 net/ipv4/ping.c                         |   1 +
 net/ipv4/tcp_ipv4.c                     |   1 +
 net/ipv4/udp.c                          |   1 +
 net/ipv6/af_inet6.c                     |   2 +
 net/ipv6/ping.c                         |   1 +
 net/ipv6/tcp_ipv6.c                     |   1 +
 net/ipv6/udp.c                          |   1 +
 tools/testing/selftests/bpf/test_sock.c | 370 ++++++++++++++----------
 10 files changed, 233 insertions(+), 148 deletions(-)

-- 
2.27.0