linux-kernel - [PATCH v2] ipv4: netfilter: ipt_CLUSTERIP: fix buffer overflow

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Message-ID: <20110317113229.GA7710@albatros>
Date:	Thu, 17 Mar 2011 14:32:29 +0300
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Changli Gao <xiaosuo@...il.com>, linux-kernel@...r.kernel.org,
	security@...nel.org, "David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org
Subject: [PATCH v2] ipv4: netfilter: ipt_CLUSTERIP: fix buffer overflow

'buffer' string is copied from userspace.  It is not checked whether it is
zero terminated.  This may lead to overflow inside of simple_strtoul().
Changli Gao suggested to copy not more than user supplied 'size' bytes.

It was introduced before the git epoch.  Files "ipt_CLUSTERIP/*" are
root writable only by default, however, on some setups permissions might be
relaxed to e.g. network admin user.

Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com>
---
 net/ipv4/netfilter/ipt_CLUSTERIP.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c
index 1e26a48..af7dec6 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -669,8 +669,11 @@ static ssize_t clusterip_proc_write(struct file *file, const char __user *input,
 	char buffer[PROC_WRITELEN+1];
 	unsigned long nodenum;
 
-	if (copy_from_user(buffer, input, PROC_WRITELEN))
+	if (size > PROC_WRITELEN)
+		return -EIO;
+	if (copy_from_user(buffer, input, size))
 		return -EFAULT;
+	buffer[size] = 0;
 
 	if (*buffer == '+') {
 		nodenum = simple_strtoul(buffer+1, NULL, 10);
-- 
1.7.0.4
--
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