netdev - Re: [PATCH net] sctp: do not check port in sctp_inet6_cmp

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Date:   Wed, 11 Apr 2018 15:59:26 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        network dev <netdev@...r.kernel.org>,
        linux-sctp@...r.kernel.org, davem <davem@...emloft.net>
Subject: Re: [PATCH net] sctp: do not check port in sctp_inet6_cmp_addr

On Thu, Apr 12, 2018 at 12:16:58AM +0800, Xin Long wrote:
> On Wed, Apr 11, 2018 at 10:59 PM, Marcelo Ricardo Leitner
> <marcelo.leitner@...il.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@...hat.com>
> >> > Signed-off-by: Xin Long <lucien.xin@...il.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)
Yes, I'd be ok with that
Neil

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