linux-kernel - Re: net/netfilter/xt_LOG.c:43: error: format not a string literal and no format arguments

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Date:	Mon, 30 Jun 2014 11:06:23 -0700
From:	Kees Cook <keescook@...gle.com>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: net/netfilter/xt_LOG.c:43: error: format not a string literal and
 no format arguments

On Mon, Jun 30, 2014 at 10:39 AM, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> On Mon, Jun 30, 2014 at 10:05:01AM -0700, Kees Cook wrote:
>> On Sat, Jun 28, 2014 at 7:07 AM, Fengguang Wu <fengguang.wu@...el.com> wrote:
>> > tree:   git://internal_merge_and_test_tree devel-ant-um-201406281943
>> > head:   fbb9065499371b760e0543f2ff66fde4778b46ae
>> > commit: 2af37708d3ce0ae78898051ea76bc7c5f683171c [30/31] Merge 'nftables/master' into devel-ant-um-201406281943
>> > config: make ARCH=avr32 atngw100_defconfig
>> >
>> > All error/warnings:
>> >
>> >    net/netfilter/xt_LOG.c: In function 'log_tg':
>> >>> net/netfilter/xt_LOG.c:43: error: format not a string literal and no format arguments
>> >
>> > vim +43 net/netfilter/xt_LOG.c
>> >
>> > 6939c33a Richard Weinberger 2012-02-10  27  #include <linux/netfilter/xt_LOG.h>
>> > 6939c33a Richard Weinberger 2012-02-10  28  #include <linux/netfilter_ipv6/ip6_tables.h>
>> > 6939c33a Richard Weinberger 2012-02-10  29  #include <net/netfilter/nf_log.h>
>> > 6939c33a Richard Weinberger 2012-02-10  30
>> > 6939c33a Richard Weinberger 2012-02-10  31  static unsigned int
>> > 6939c33a Richard Weinberger 2012-02-10  32  log_tg(struct sk_buff *skb, const struct xt_action_param *par)
>> > 6939c33a Richard Weinberger 2012-02-10  33  {
>> > 6939c33a Richard Weinberger 2012-02-10  34      const struct xt_log_info *loginfo = par->targinfo;
>> > 6939c33a Richard Weinberger 2012-02-10  35      struct nf_loginfo li;
>> > 8cdb46da Hans Schillstrom   2013-05-15  36      struct net *net = dev_net(par->in ? par->in : par->out);
>> > 6939c33a Richard Weinberger 2012-02-10  37
>> > 6939c33a Richard Weinberger 2012-02-10  38      li.type = NF_LOG_TYPE_LOG;
>> > 6939c33a Richard Weinberger 2012-02-10  39      li.u.log.level = loginfo->level;
>> > 6939c33a Richard Weinberger 2012-02-10  40      li.u.log.logflags = loginfo->logflags;
>> > 6939c33a Richard Weinberger 2012-02-10  41
>> > fab4085f Pablo Neira Ayuso  2014-06-18  42      nf_log_packet(net, par->family, par->hooknum, skb, par->in, par->out,
>> > fab4085f Pablo Neira Ayuso  2014-06-18 @43                    &li, loginfo->prefix);
>>
>> This needs to be:
>>
>> nf_log_packet(net, par->family, par->hooknum, skb, par->in, par->out,
>>                      &li, "%s", loginfo->prefix);
>>
>> Without this, any format strings contained by "prefix" can get
>> processed and leak kernel contents.
>
>
> http://git.kernel.org/cgit/linux/kernel/git/pablo/nf-next.git/commit/?id=ca1aa54f272d47bec77baa292f803df7a81f966b

Ah-ha! Perfect, thanks! :)

-Kees

-- 
Kees Cook
Chrome OS Security
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