[PATCH 1/2] cipso: fix total option length computation
Ondrej Mosnacek
omosnace at redhat.com
Wed Apr 17 12:49:23 UTC 2024
On Tue, Apr 16, 2024 at 8:39 PM Paul Moore <paul at paul-moore.com> wrote:
>
> On Apr 16, 2024 Ondrej Mosnacek <omosnace at redhat.com> wrote:
> >
> > As evident from the definition of ip_options_get(), the IP option
> > IPOPT_END is used to pad the IP option data array, not IPOPT_NOP. Yet
> > the loop that walks the IP options to determine the total IP options
> > length in cipso_v4_delopt() doesn't take it into account.
> >
> > Fix it by recognizing the IPOPT_END value as the end of actual options.
> > Also add safety checks in case the options are invalid/corrupted.
> >
> > Fixes: 014ab19a69c3 ("selinux: Set socket NetLabel based on connection endpoint")
> > Signed-off-by: Ondrej Mosnacek <omosnace at redhat.com>
> > ---
> > net/ipv4/cipso_ipv4.c | 19 ++++++++++++++-----
> > 1 file changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
> > index 8b17d83e5fde4..75b5e3c35f9bf 100644
> > --- a/net/ipv4/cipso_ipv4.c
> > +++ b/net/ipv4/cipso_ipv4.c
> > @@ -2012,12 +2012,21 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
> > * from there we can determine the new total option length */
> > iter = 0;
> > optlen_new = 0;
> > - while (iter < opt->opt.optlen)
> > - if (opt->opt.__data[iter] != IPOPT_NOP) {
> > - iter += opt->opt.__data[iter + 1];
> > - optlen_new = iter;
> > - } else
> > + while (iter < opt->opt.optlen) {
> > + if (opt->opt.__data[iter] == IPOPT_END) {
> > + break;
> > + } else if (opt->opt.__data[iter] == IPOPT_NOP) {
> > iter++;
> > + } else {
> > + if (WARN_ON(opt->opt.__data[iter + 1] < 2))
> > + iter += 2;
> > + else
> > + iter += opt->opt.__data[iter + 1];
> > + optlen_new = iter;
>
> I worry that WARN_ON(), especially in conjunction with the one below,
> could generate a lot of noise on the console and system logs, let's
> be a bit more selective about what we check and report on. Presumably
> the options have already gone through a basic sanity check so there
> shouldn't be anything too scary in there.
>
> if (opt == IPOPT_END) {
> /* ... */
> } else if (opt == IPOPT_NOP) {
> /* ... */
> } else {
> iter += opt[iter + 1];
> optlen_new = iter;
> }
How about turning it to WARN_ON_ONCE() instead? It's actually the
better choice in this case (alerts to a possible kernel bug, not to an
event that would need to be logged every time), I just used WARN_ON()
instinctively and didn't think of the _ONCE variant.
>
> > + }
> > + }
> > + if (WARN_ON(optlen_new > opt->opt.optlen))
> > + optlen_new = opt->opt.optlen;
>
> This is also probably not really necessary, but it bothers me less.
I would convert this one to WARN_ON_ONCE() as well, or drop both if
you still don't like either of them to be there.
>
> > hdr_delta = opt->opt.optlen;
> > opt->opt.optlen = (optlen_new + 3) & ~3;
> > hdr_delta -= opt->opt.optlen;
> > --
> > 2.44.0
>
> --
> paul-moore.com
>
--
Ondrej Mosnacek
Senior Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.
More information about the Linux-security-module-archive
mailing list