From:   menglong8.dong@gmail.com
To:     kuba@kernel.org, daniel@iogearbox.net
Cc:     davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org,
        edumazet@google.com, shuah@kernel.org, ast@kernel.org,
        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 v3 net-next 0/2] net: bpf: handle return value of post_bind{4,6} and add selftests for it
Date:   Wed,  5 Jan 2022 21:18:47 +0800
Message-Id: <20220105131849.2559506-1-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.

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 (2):
  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}

 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 | 166 +++++++++++++++++++++---
 10 files changed, 157 insertions(+), 20 deletions(-)

-- 
2.27.0