linux-kernel - [PATCH] 4 bytes kernel memory disclosure in SO

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Message-ID: <20090212123545.GA46788@clem1.netasq.com>
Date:	Thu, 12 Feb 2009 13:35:45 +0100
From:	Clement LECIGNE <clement.lecigne@...asq.com>
To:	linux-kernel@...r.kernel.org
Cc:	netdev@...r.kernel.org
Subject: [PATCH] 4 bytes kernel memory disclosure in SO_BSDCOMPAT gsopt try
	#2

Hi,

In function sock_getsockopt() located in net/core/sock.c, optval v.val
is not correctly initialized and directly returned in userland in case
we have SO_BSDCOMPAT option set.

This dummy code should trigger the bug:

int main(void)
{
	unsigned char buf[4] = { 0, 0, 0, 0 };
	int len;
	int sock;
	sock = socket(33, 2, 2);
	getsockopt(sock, 1, SO_BSDCOMPAT, &buf, &len);
	printf("%x%x%x%x\n", buf[0], buf[1], buf[2], buf[3]);
	close(sock);
}

Here is a patch that fix this bug by initalizing v.val just after its declaration.

--- linux/net/core/sock.c.orig	2008-12-12 12:27:46.000000000 -0800
+++ linux/net/core/sock.c	2008-12-12 12:27:50.000000000 -0800
@@ -695,6 +695,8 @@ int sock_getsockopt(struct socket *sock,
 	if (len < 0)
 		return -EINVAL;
 
+	v.val = 0;
+
 	switch(optname) {
 	case SO_DEBUG:
 		v.val = sock_flag(sk, SOCK_DBG);

Signed-off-by: Clément Lecigne <clement.lecigne@...asq.com>

-- 
Clément LECIGNE,
"In Python, how do you create a string of random characters?" -- "Read a Perl file!"
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