On Fri, Apr 27, 2018 at 05:39:06PM +0200, Guillaume Nault wrote:
> On Fri, Apr 27, 2018 at 08:23:16AM -0400, Kevin Easton wrote:
...
> > There's another bug here - pppoe_connect() should also be validating
> > sp->sa_family. My suggested patch was going to be:
> >
> > diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> > index 1483bc7..90eb3fd 100644
> > --- a/drivers/net/ppp/pppoe.c
> > +++ b/drivers/net/ppp/pppoe.c
> > @@ -620,6 +620,14 @@ static int pppoe_connect(struct socket *sock, struct
> > sockaddr *uservaddr,
> > lock_sock(sk);
> >
> > error = -EINVAL;
> > + if (sockaddr_len < sizeof(struct sockaddr_pppox))
> > + goto end;
> > +
> > + error = -EAFNOSUPPORT;
> > + if (sp->sa_family != AF_PPPOX)
> > + goto end;
> > +
> > + error = -EINVAL;
> > if (sp->sa_protocol != PX_PROTO_OE)
> > goto end;
> >
> > Should I rework this on top of net.git HEAD?
> >
> > (The same applies to pppol2tp_connect()).
> >
> Thanks for the suggestion. But ->sa_family has never been checked.
> Therefore, it has always been possible to connect a PPPoE or L2TP
> socket with an invalid .sa_family field. I'd be surprised if there were
> implementations relying on that, but we never know (for example, an
> implementation could send this field uninitialised). By being stricter
> we'd break such programs. And we don't need this field in the
> connection process, so not checking its value doesn't harm.
>
> I'm all for being strict and validating user-provided data as much as
> possible, but I'm afraid its too late in this case.
Doesn't the same apply to supplying a bogus sockaddr_len?
I did test the rp-pppoe plugin for pppd with this patch - it does
correctly set both the sa_family and sockaddr_len. Checking on
Debian's codesearch also showed that everything in that corpus
that uses PX_PROTO_OE also sets AF_PPPOX.
- Kevin
>
