On Sat, Feb 1, 2020 at 10:16 PM Florian Westphal <fw@xxxxxxxxx> wrote:
>
> Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> > > In order to prevent breaking userspace, perhaps make it so that the
> > > kernel caps cfg.max at twice that value? Would allow storing up to
> > > 16777216 addresses with an average chain depth of 16 (which is quite
> > > large). We could increase the max limit in case someone presents a use
> > > case.
> > >
> >
> > Not sure if I understand this, I don't see how cap'ing cfg->max could
> > help prevent breaking user-space? Are you suggesting to cap it with
> > HASHLIMIT_MAX_SIZE too? Something like below?
> >
> > + if (cfg->max > 2 * HASHLIMIT_MAX_SIZE)
> > + cfg->max = 2 * HASHLIMIT_MAX_SIZE;
> >
>
> Yes, thats what I meant, cap the user-provided value to something thats
> going to be less of a problem.
>
> But now that I read it, the "2 *" part looks really silly, so I suggst
> to go with " > FOO_MAX", else its not a maximum value after all.
Ok, so here is what I have now:
+#define HASHLIMIT_MAX_SIZE 1048576
+
static int hashlimit_mt_check_common(const struct xt_mtchk_param *par,
struct xt_hashlimit_htable **hinfo,
struct hashlimit_cfg3 *cfg,
@@ -847,6 +849,14 @@ static int hashlimit_mt_check_common(const struct
xt_mtchk_param *par,
if (cfg->gc_interval == 0 || cfg->expire == 0)
return -EINVAL;
+ if (cfg->size > HASHLIMIT_MAX_SIZE) {
+ cfg->size = HASHLIMIT_MAX_SIZE;
+ pr_info_ratelimited("size too large, truncated to
%u\n", cfg->size);
+ }
+ if (cfg->max > HASHLIMIT_MAX_SIZE) {
+ cfg->max = HASHLIMIT_MAX_SIZE;
+ pr_info_ratelimited("max too large, truncated to
%u\n", cfg->max);
+ }
Please let me know if it is still different with your suggestion.
Thanks!
