From: David Ahern <dsahern@gmail.com>
Date: Wed, 10 Jan 2018 21:00:39 +0000 (-0800)
Subject: netlink: extack needs to be reset each time through loop
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3eae0ba8c9b51d83d2293249fb9c82e90fc6dc31;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

netlink: extack needs to be reset each time through loop


[ Upstream commit cbbdf8433a5f117b1a2119ea30fc651b61ef7570 ]

syzbot triggered the WARN_ON in netlink_ack testing the bad_attr value.
The problem is that netlink_rcv_skb loops over the skb repeatedly invoking
the callback and without resetting the extack leaving potentially stale
data. Initializing each time through avoids the WARN_ON.

Fixes: 2d4bc93368f5a ("netlink: extended ACK reporting")
Reported-by: syzbot+315fa6766d0f7c359327@syzkaller.appspotmail.com
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index aac9d68b4636..f4eb3fe59fe5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2393,7 +2393,7 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
 						   struct nlmsghdr *,
 						   struct netlink_ext_ack *))
 {
-	struct netlink_ext_ack extack = {};
+	struct netlink_ext_ack extack;
 	struct nlmsghdr *nlh;
 	int err;
 
@@ -2414,6 +2414,7 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
 		if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
 			goto ack;
 
+		memset(&extack, 0, sizeof(extack));
 		err = cb(skb, nlh, &extack);
 		if (err == -EINTR)
 			goto skip;