Re: [PATCH 2/6] netlink: have netlink per-protocol bind function return an error code.

Richard Guy Briggs
2014-04-23T01:30:05Z

On 14/04/22, David Miller wrote:
> From: Richard Guy Briggs <rgb@redhat.com>
> Date: Fri, 18 Apr 2014 13:34:06 -0400
>
> > @@ -1449,6 +1453,26 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
> > if (!nladdr->nl_groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))
> > return 0;
> >
> > + if (nlk->netlink_bind && nladdr->nl_groups) {
> > + int i;
> > +
> > + for (i = 0; i < nlk->ngroups; i++) {
> > + int undo;
> > +
> > + if (!test_bit(i, (long unsigned int *)&nladdr->nl_groups))
> > + continue;
> > + err = nlk->netlink_bind(i);
> > + if (!err)
> > + continue;
> > + if (!nlk->portid)
> > + netlink_remove(sk);
> > + for (undo = 0; undo < i; undo++)
> > + if (nlk->netlink_unbind)
> > + nlk->netlink_unbind(undo);
> > + return err;
> > + }
> > + }
> > +
>
> It took me a while to figure out why you need to do the netlink_remove() in
> the error path.
>
> I think it's really asking for trouble to allow the socket to have temporary
> visibility if we end up signalling an error.

The risk seems small, but I agree it is sloppy.

> It seems safest if we only do the autobind/insert once we are absolutely
> certain that the bind() will fully succeed. This means that you have to
> do this bind validation loop before autobind/insert.

Ok, done. This revision ends up being a bit cleaner than the previous
one because I've refactored out the unbind loop into netlink_unbind()
due to it needing to be called if the netlink_insert/autobind() fails as
well. In the factorization process I noticed that unrequested groups
were being unnecessarily unbound. It also provoked assigning the var
"groups" from "nladdr->nl_groups" making things easier to read.

> Please make this change and resubmit this series, thanks.

Compiled and tested. New patchset to follow.

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
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