[backport request] netfilter: ipt_ULOG: fix info leaks

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Hi,

apparently the below commit didn't find its way to -stable. Please
backport this quite straightforward fix to a blatant and by now rather
old information leak issue. Applies cleanly to anything above 3.4. 3.4
and down requires very minor tweaks.

Thanks!

===

From 278f2b3e2af5f32ea1afe34fa12a2518153e6e49 Mon Sep 17 00:00:00 2001
From: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Date: Mon, 30 Sep 2013 22:05:08 +0200
Subject: [PATCH] netfilter: ipt_ULOG: fix info leaks

The ulog messages leak heap bytes by the means of padding bytes and
incompletely filled string arrays. Fix those by memset(0)'ing the
whole struct before filling it.

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
 net/ipv4/netfilter/ipt_ULOG.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_ULOG.c b/net/ipv4/netfilter/ipt_ULOG.c
index cbc2215..9cb993c 100644
--- a/net/ipv4/netfilter/ipt_ULOG.c
+++ b/net/ipv4/netfilter/ipt_ULOG.c
@@ -220,6 +220,7 @@ static void ipt_ulog_packet(struct net *net,
 	ub->qlen++;
 
 	pm = nlmsg_data(nlh);
+	memset(pm, 0, sizeof(*pm));
 
 	/* We might not have a timestamp, get one */
 	if (skb->tstamp.tv64 == 0)
@@ -238,8 +239,6 @@ static void ipt_ulog_packet(struct net *net,
 	}
 	else if (loginfo->prefix[0] != '\0')
 		strncpy(pm->prefix, loginfo->prefix, sizeof(pm->prefix));
-	else
-		*(pm->prefix) = '\0';
 
 	if (in && in->hard_header_len > 0 &&
 	    skb->mac_header != skb->network_header &&
@@ -251,13 +250,9 @@ static void ipt_ulog_packet(struct net *net,
 
 	if (in)
 		strncpy(pm->indev_name, in->name, sizeof(pm->indev_name));
-	else
-		pm->indev_name[0] = '\0';
 
 	if (out)
 		strncpy(pm->outdev_name, out->name, sizeof(pm->outdev_name));
-	else
-		pm->outdev_name[0] = '\0';
 
 	/* copy_len <= skb->len, so can't fail. */
 	if (skb_copy_bits(skb, 0, pm->payload, copy_len) < 0)
-- 
2.0.0

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