From 43da5f2e0d0c69ded3d51907d9552310a6b545e8 Mon Sep 17 00:00:00 2001
From: Mathias Krause <minipli@googlemail.com>
Date: Wed, 15 Aug 2012 11:31:57 +0000
Subject: net: fix info leak in compat dev_ifconf()

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@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/socket.c b/net/socket.c
index dfe5b66..a5471f8 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2657,6 +2657,7 @@ 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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