From: Florian Westphal <fw@strlen.de>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Florian Westphal <fw@strlen.de>,
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 07:16:11 +0100 [thread overview]
Message-ID: <20200202061611.GN795@breakpoint.cc> (raw)
In-Reply-To: <CAM_iQpWbejoFPbFDSfUtvhFbU3DjhV6NAkPQ+-mirY_QEMHxkA@mail.gmail.com>
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.
next prev parent reply other threads:[~2020-02-02 6:16 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 [this message]
2020-02-02 18:27 ` Cong Wang
2020-02-02 22:37 ` Florian Westphal
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