[PATCH 4.9 21/44] net/appletalk: fix minor pointer leak to userspace in SIOCFINDIPDDPRT

[Greg Kroah-Hartman]

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

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

From: Willy Tarreau <w@xxxxxx>

[ Upstream commit 9824dfae5741275473a23a7ed5756c7b6efacc9d ]

Fields ->dev and ->next of struct ipddp_route may be copied to
userspace on the SIOCFINDIPDDPRT ioctl. This is only accessible
to CAP_NET_ADMIN though. Let's manually copy the relevant fields
instead of using memcpy().

BugLink: http://blog.infosectcbr.com.au/2018/09/linux-kernel-infoleaks.html
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/appletalk/ipddp.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/net/appletalk/ipddp.c
+++ b/drivers/net/appletalk/ipddp.c
@@ -284,8 +284,12 @@ static int ipddp_ioctl(struct net_device
                 case SIOCFINDIPDDPRT:
 			spin_lock_bh(&ipddp_route_lock);
 			rp = __ipddp_find_route(&rcp);
-			if (rp)
-				memcpy(&rcp2, rp, sizeof(rcp2));
+			if (rp) {
+				memset(&rcp2, 0, sizeof(rcp2));
+				rcp2.ip    = rp->ip;
+				rcp2.at    = rp->at;
+				rcp2.flags = rp->flags;
+			}
 			spin_unlock_bh(&ipddp_route_lock);
 
 			if (rp) {