netdev - [PATCH] net/appletalk: fix minor pointer leak to userspace in SIOCFINDIPDDPRT

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Message-ID: <20180912053635.GA21168@1wt.eu>
Date:   Wed, 12 Sep 2018 07:36:35 +0200
From:   Willy Tarreau <w@....eu>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jann Horn <jannh@...gle.com>
Subject: [PATCH] net/appletalk: fix minor pointer leak to userspace in
 SIOCFINDIPDDPRT

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@...gle.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/net/appletalk/ipddp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/appletalk/ipddp.c b/drivers/net/appletalk/ipddp.c
index 9375cef..3d27616 100644
--- a/drivers/net/appletalk/ipddp.c
+++ b/drivers/net/appletalk/ipddp.c
@@ -283,8 +283,12 @@ static int ipddp_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
                 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) {
-- 
2.8.0.rc2.1.gbe9624a