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: Fri, 31 Jan 2020 18:53:21 -0800 [thread overview]
Message-ID: <CAM_iQpWbejoFPbFDSfUtvhFbU3DjhV6NAkPQ+-mirY_QEMHxkA@mail.gmail.com> (raw)
In-Reply-To: <20200131233659.GM795@breakpoint.cc>
On Fri, Jan 31, 2020 at 3:37 PM Florian Westphal <fw@strlen.de> wrote:
> O would propose a max alloc size (hard limit) of ~8 MByte of vmalloc
> space, or maybe 16 at most.
>
> 1048576 max upperlimit -> ~8mbyte vmalloc request -> allows to store
> up to 2**23 entries.
Changing HASHLIMIT_MAX_SIZE to 1048576 seems fine.
>
> 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;
Thanks.
next prev parent reply other threads:[~2020-02-01 2:53 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 [this message]
2020-02-02 6:16 ` Florian Westphal
2020-02-02 18:27 ` Cong Wang
2020-02-02 22:37 ` Florian Westphal
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