• Menglong Dong's avatar
    net: bpf: Handle return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND() · 91a760b2
    Menglong Dong authored
    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: default avatarMenglong Dong <imagedong@tencent.com>
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Link: https://lore.kernel.org/bpf/20220106132022.3470772-2-imagedong@tencent.com
    91a760b2
udp.c 45 KB