[hardy CVE 1/1] netfilter: ipt_CLUSTERIP: fix buffer overflow

Andy Whitcroft apw at canonical.com
Thu Jul 7 09:28:05 UTC 2011

From: Vasiliy Kulikov <segoon at openwall.com>

'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 at openwall.com>
Acked-by: Changli Gao <xiaosuo at gmail.com>
Signed-off-by: Patrick McHardy <kaber at trash.net>

(cherry picked from commit 961ed183a9fd080cf306c659b8736007e44065a5)
BugLink: http://bugs.launchpad.net/bugs/801473
Signed-off-by: Andy Whitcroft <apw at canonical.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 2f544da..6420953 100644
--- a/net/ipv4/netfilter/ipt_CLUSTERIP.c
+++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c
@@ -686,8 +686,11 @@ static ssize_t clusterip_proc_write(struct file *file, const char __user *input,
 	struct clusterip_config *c = pde->data;
 	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);

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