netdev - Re: [PATCH] ipv4: netfilter: always let NUL terminated string ended by '\0'

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Date:	Thu, 23 May 2013 13:49:50 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	kaber@...sh.net, kuznet@....inr.ac.ru, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, David Miller <davem@...emloft.net>,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipv4: netfilter: always let NUL terminated string ended
 by '\0'

On Thu, May 23, 2013 at 07:39:39PM +0800, Chen Gang wrote:
> On 05/23/2013 07:08 PM, Pablo Neira Ayuso wrote:
> > On Fri, May 17, 2013 at 04:39:15PM +0800, Chen Gang wrote:
> >> >
> >> > For NUL terminated string, better always be sure of ended by '\0'.
> >> >
> >> > 'pm' is 'struct ulog_packet_msg_t' which may be copied to user mode
> >> > (defined in "include/uapi/..."), so can not use strlcpy() instead of.
> > loginfo->prefix is always nul-terminated, as this is validated in
> > checkentry. I don't think the kernel will take a non nul-terminated
> > device name either.
>
> Really it is.
>
> And 'prefix' max length is 128 (NF_LOG_PREFIXLEN), and 'pm->prefix' max
> length is 32 (ULOG_PREFIX_LEN), so we still need this patch, but need
> improved.

Both are ULOG_PREFIX_LEN long.

>From include/uapi/linux/netfilter_ipv4/ipt_ULOG.h:

/* private data structure for each rule with a ULOG target */
struct ipt_ulog_info {
        unsigned int nl_group;
        size_t copy_range;
        size_t qthreshold;
        char prefix[ULOG_PREFIX_LEN];
};

/* Format of the ULOG packets passed through netlink */
typedef struct ulog_packet_msg {
        unsigned long mark;
        long timestamp_sec;
        long timestamp_usec;
        unsigned int hook;
        char indev_name[IFNAMSIZ];
        char outdev_name[IFNAMSIZ];
        size_t data_len;
        char prefix[ULOG_PREFIX_LEN];
        unsigned char mac_len;
        unsigned char mac[ULOG_MAC_LEN;
        unsigned char payload[0];
} ulog_packet_msg_t;
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