From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Wed, 26 Feb 2020 18:47:34 +0000 (+0100)
Subject: netlink: Use netlink header as base to calculate bad attribute offset
X-Git-Tag: v5.6-rc6~23^2~67
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=84b3268027641401bb8ad4427a90a3cce2eb86f5;p=linux.git

netlink: Use netlink header as base to calculate bad attribute offset

Userspace might send a batch that is composed of several netlink
messages. The netlink_ack() function must use the pointer to the netlink
header as base to calculate the bad attribute offset.

Fixes: 2d4bc93368f5 ("netlink: extended ACK reporting")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index edf3e285e242..5313f1cec170 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2434,7 +2434,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 							       in_skb->len))
 				WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
 						    (u8 *)extack->bad_attr -
-						    in_skb->data));
+						    (u8 *)nlh));
 		} else {
 			if (extack->cookie_len)
 				WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,