linux-kernel - [ 068/135] net: fix info leak in compat dev

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Message-Id: <20120917003635.622842551@decadent.org.uk>
Date:	Mon, 17 Sep 2012 01:37:33 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Mathias Krause <minipli@...glemail.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 068/135] net: fix info leak in compat dev_ifconf()

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mathias Krause <minipli@...glemail.com>

[ Upstream commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8 ]

The implementation of dev_ifconf() for the compat ioctl interface uses
an intermediate ifc structure allocated in userland for the duration of
the syscall. Though, it fails to initialize the padding bytes inserted
for alignment and that for leaks four bytes of kernel stack. Add an
explicit memset(0) before filling the structure to avoid the info leak.

Signed-off-by: Mathias Krause <minipli@...glemail.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/socket.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/socket.c b/net/socket.c
index 273cbce..68879db 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2645,6 +2645,7 @@ static int dev_ifconf(struct net *net, struct compat_ifconf __user *uifc32)
 	if (copy_from_user(&ifc32, uifc32, sizeof(struct compat_ifconf)))
 		return -EFAULT;
 
+	memset(&ifc, 0, sizeof(ifc));
 	if (ifc32.ifcbuf == 0) {
 		ifc32.ifc_len = 0;
 		ifc.ifc_len = 0;


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