[CVE-2016-4580][precise, trusty, lts-utopic, vivid, wily] net: fix a kernel infoleak in x25 module

[Luis Henriques]

From: Kangjie Lu <kangjielu at gmail.com>

Stack object "dte_facilities" is allocated in x25_rx_call_request(),
which is supposed to be initialized in x25_negotiate_facilities.
However, 5 fields (8 bytes in total) are not initialized. This
object is then copied to userland via copy_to_user, thus infoleak
occurs.

Signed-off-by: Kangjie Lu <kjlu at gatech.edu>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 79e48650320e6fba48369fccf13fd045315b19b8)
CVE-2016-4580
BugLink: https://bugs.launchpad.net/bugs/1585366
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/x25/x25_facilities.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c
index 36384a1fa9f2..887749c8054d 100644
--- a/net/x25/x25_facilities.c
+++ b/net/x25/x25_facilities.c
@@ -271,6 +271,7 @@ int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
 
 	memset(&theirs, 0, sizeof(theirs));
 	memcpy(new, ours, sizeof(*new));
+	memset(dte, 0, sizeof(*dte));
 
 	len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
 	if (len < 0)