From: Cong Wang <xiyou.wangcong@gmail.com>
To: Florian Westphal <fw@strlen.de>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
NetFilter <netfilter-devel@vger.kernel.org>,
syzbot <syzbot+adf6c6c2be1c3a718121@syzkaller.appspotmail.com>,
Pablo Neira Ayuso <pablo@netfilter.org>,
Jozsef Kadlecsik <kadlec@netfilter.org>
Subject: Re: [Patch nf 3/3] xt_hashlimit: limit the max size of hashtable
Date: Sun, 2 Feb 2020 10:27:34 -0800 [thread overview]
Message-ID: <CAM_iQpXC9FnisZwLwWHQEbi-She3HywO5SJAxSS1cf_Pntn-6Q@mail.gmail.com> (raw)
In-Reply-To: <20200202061611.GN795@breakpoint.cc>
On Sat, Feb 1, 2020 at 10:16 PM Florian Westphal <fw@strlen.de> wrote:
>
> Cong Wang <xiyou.wangcong@gmail.com> 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!
next prev parent reply other threads:[~2020-02-02 18:28 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 20:52 [Patch nf 0/3] netfilter: xt_hashlimit: a few improvements Cong Wang
2020-01-31 20:52 ` [Patch nf 1/3] xt_hashlimit: avoid OOM for user-controlled vmalloc Cong Wang
2020-01-31 22:08 ` Florian Westphal
2020-01-31 23:17 ` Cong Wang
2020-01-31 20:52 ` [Patch nf 2/3] xt_hashlimit: reduce hashlimit_mutex scope for htable_put() Cong Wang
2020-01-31 22:09 ` Florian Westphal
2020-01-31 20:52 ` [Patch nf 3/3] xt_hashlimit: limit the max size of hashtable Cong Wang
2020-01-31 22:08 ` Florian Westphal
2020-01-31 23:16 ` Cong Wang
2020-01-31 23:36 ` Florian Westphal
2020-02-01 2:53 ` Cong Wang
2020-02-02 6:16 ` Florian Westphal
2020-02-02 18:27 ` Cong Wang [this message]
2020-02-02 22:37 ` Florian Westphal
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