From: Florian Westphal <fw@strlen.de>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: netdev@vger.kernel.org, netfilter-devel@vger.kernel.org,
syzbot+adf6c6c2be1c3a718121@syzkaller.appspotmail.com,
Pablo Neira Ayuso <pablo@netfilter.org>,
Jozsef Kadlecsik <kadlec@netfilter.org>,
Florian Westphal <fw@strlen.de>
Subject: Re: [Patch nf 3/3] xt_hashlimit: limit the max size of hashtable
Date: Fri, 31 Jan 2020 23:08:07 +0100 [thread overview]
Message-ID: <20200131220807.GJ795@breakpoint.cc> (raw)
In-Reply-To: <20200131205216.22213-4-xiyou.wangcong@gmail.com>
Cong Wang <xiyou.wangcong@gmail.com> wrote:
> The user-specified hashtable size is unbound, this could
> easily lead to an OOM or a hung task as we hold the global
> mutex while allocating and initializing the new hashtable.
>
> The max value is derived from the max value when chosen by
> the kernel.
>
> Reported-and-tested-by: syzbot+adf6c6c2be1c3a718121@syzkaller.appspotmail.com
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
> Cc: Florian Westphal <fw@strlen.de>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
> net/netfilter/xt_hashlimit.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
> index 57a2639bcc22..6327134c5886 100644
> --- a/net/netfilter/xt_hashlimit.c
> +++ b/net/netfilter/xt_hashlimit.c
> @@ -272,6 +272,8 @@ dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent)
> }
> static void htable_gc(struct work_struct *work);
>
> +#define HASHLIMIT_MAX_SIZE 8192
> +
> static int htable_create(struct net *net, struct hashlimit_cfg3 *cfg,
> const char *name, u_int8_t family,
> struct xt_hashlimit_htable **out_hinfo,
> @@ -290,7 +292,7 @@ static int htable_create(struct net *net, struct hashlimit_cfg3 *cfg,
> size = (nr_pages << PAGE_SHIFT) / 16384 /
> sizeof(struct hlist_head);
> if (nr_pages > 1024 * 1024 * 1024 / PAGE_SIZE)
> - size = 8192;
> + size = HASHLIMIT_MAX_SIZE;
> if (size < 16)
> size = 16;
> }
> @@ -848,6 +850,8 @@ 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)
> + return -ENOMEM;
Hmm, won't that break restore of rulesets that have something like
--hashlimit-size 10000?
AFAIU this limits the module to vmalloc requests of only 64kbyte.
I'm not opposed to a limit (or a cap), but 64k seems a bit low to me.
next prev parent reply other threads:[~2020-01-31 22:08 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 [this message]
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
2020-02-02 22:37 ` Florian Westphal
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