Re: [PATCH net] sctp: do not check port in sctp_inet6_cmp_addr

[Xin Long <lucien.xin@gmail.com>]

On Wed, Apr 11, 2018 at 10:59 PM, Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
> On Wed, Apr 11, 2018 at 10:36:07AM -0400, Neil Horman wrote:
>> On Wed, Apr 11, 2018 at 08:58:05PM +0800, Xin Long wrote:
>> > pf->cmp_addr() is called before binding a v6 address to the sock. It
>> > should not check ports, like in sctp_inet_cmp_addr.
>> >
>> > But sctp_inet6_cmp_addr checks the addr by invoking af(6)->cmp_addr,
>> > sctp_v6_cmp_addr where it also compares the ports.
>> >
>> > This would cause that setsockopt(SCTP_SOCKOPT_BINDX_ADD) could bind
>> > multiple duplicated IPv6 addresses after Commit 40b4f0fd74e4 ("sctp:
>> > lack the check for ports in sctp_v6_cmp_addr").
>> >
>> > This patch is to remove af->cmp_addr called in sctp_inet6_cmp_addr,
>> > but do the proper check for both v6 addrs and v4mapped addrs.
>> >
>> > Fixes: 40b4f0fd74e4 ("sctp: lack the check for ports in sctp_v6_cmp_addr")
>> > Reported-by: Jianwen Ji <jiji@redhat.com>
>> > Signed-off-by: Xin Long <lucien.xin@gmail.com>
>> > ---
>> >  net/sctp/ipv6.c | 27 ++++++++++++++++++++++++---
>> >  1 file changed, 24 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
>> > index f1fc48e..be4b72c 100644
>> > --- a/net/sctp/ipv6.c
>> > +++ b/net/sctp/ipv6.c
>> > @@ -846,8 +846,8 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
>> >                            const union sctp_addr *addr2,
>> >                            struct sctp_sock *opt)
>> >  {
>> > -   struct sctp_af *af1, *af2;
>> >     struct sock *sk = sctp_opt2sk(opt);
>> > +   struct sctp_af *af1, *af2;
>> >
>> >     af1 = sctp_get_af_specific(addr1->sa.sa_family);
>> >     af2 = sctp_get_af_specific(addr2->sa.sa_family);
>> > @@ -863,10 +863,31 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
>> >     if (sctp_is_any(sk, addr1) || sctp_is_any(sk, addr2))
>> >             return 1;
>> >
>> > -   if (addr1->sa.sa_family != addr2->sa.sa_family)
>> > +   if (addr1->sa.sa_family != addr2->sa.sa_family) {
>> > +           if (addr1->sa.sa_family == AF_INET &&
>> > +               addr2->sa.sa_family == AF_INET6 &&
>> > +               ipv6_addr_v4mapped(&addr2->v6.sin6_addr))
>> > +                   if (addr2->v6.sin6_addr.s6_addr32[3] ==
>> > +                       addr1->v4.sin_addr.s_addr)
>> > +                           return 1;
>> > +           if (addr2->sa.sa_family == AF_INET &&
>> > +               addr1->sa.sa_family == AF_INET6 &&
>> > +               ipv6_addr_v4mapped(&addr1->v6.sin6_addr))
>> > +                   if (addr1->v6.sin6_addr.s6_addr32[3] ==
>> > +                       addr2->v4.sin_addr.s_addr)
>> > +                           return 1;
>> > +           return 0;
>> > +   }
>> > +
>> > +   if (!ipv6_addr_equal(&addr1->v6.sin6_addr, &addr2->v6.sin6_addr))
>> > +           return 0;
>> > +
>> > +   if ((ipv6_addr_type(&addr1->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) &&
>> > +       addr1->v6.sin6_scope_id && addr2->v6.sin6_scope_id &&
>> > +       addr1->v6.sin6_scope_id != addr2->v6.sin6_scope_id)
>> >             return 0;
>> >
>> > -   return af1->cmp_addr(addr1, addr2);
>> > +   return 1;
>> >  }
>> >
>> >  /* Verify that the provided sockaddr looks bindable.   Common verification,
>> > --
>> > 2.1.0
>> >
>> This looks correct to me, but is it worth duplicating the comparison code like
>> this from the cmp_addr function?  It might be more worthwhile to add a flag to
>> the cmp_addr method to direct weather it needs to check port values or not.
>> That way you could continue to use the cmp_addr function here.
>
> Adding a flag into sctp_v6_cmp_addr will get us a terrible code to
> read. It's already not one of the best looking part of it. Maybe
> still duplicate part of it it, but at 'af' level? As in:
> - af->cmp_addr
> - af->cmp_addr_port
>
What do you think of:

static int sctp_v6_cmp_addr(const union sctp_addr *addr1,
                            const union sctp_addr *addr2)
{
        return __sctp_v6_cmp_addr(addr1, addr2) &&
               addr1->v6.sin_port == addr2->v6.sin_port;
}

(v6.sin_port and v4.sin_port have the same offset in union sctp_addr,
 we've exploited this in many places in SCTP)