Patch "netlink: extack needs to be reset each time through loop" has been added to the 4.14-stable tree

Patch "netlink: extack needs to be reset each time through loop" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    netlink: extack needs to be reset each time through loop

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     netlink-extack-needs-to-be-reset-each-time-through-loop.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Sun Jan 28 17:35:08 CET 2018
From: David Ahern <dsahern@gmail.com>
Date: Wed, 10 Jan 2018 13:00:39 -0800
Subject: netlink: extack needs to be reset each time through loop

From: David Ahern <dsahern@gmail.com>


[ 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>
---
 net/netlink/af_netlink.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2393,7 +2393,7 @@ int netlink_rcv_skb(struct sk_buff *skb,
 						   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,
 		if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
 			goto ack;
 
+		memset(&extack, 0, sizeof(extack));
 		err = cb(skb, nlh, &extack);
 		if (err == -EINTR)
 			goto skip;


Patches currently in stable-queue which might be from dsahern@gmail.com are

queue-4.14/net-ipv4-make-ip-route-get-match-iif-lo-rules-again.patch
queue-4.14/net-vrf-add-support-for-sends-to-local-broadcast-address.patch
queue-4.14/netlink-extack-needs-to-be-reset-each-time-through-loop.patch
queue-4.14/netlink-reset-extack-earlier-in-netlink_rcv_skb.patch