From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Sat, 22 Sep 2018 16:46:48 +0300
Subject: net: sched: act_ipt: check for underflow in __tcf_ipt_init()
Patch-mainline: v4.19-rc7
Git-commit: aeadd93f2b0a609f603ac33e574b97a9832d1b90
References: bsc#1109837

If "td->u.target_size" is larger than sizeof(struct xt_entry_target) we
return -EINVAL.  But we don't check whether it's smaller than
sizeof(struct xt_entry_target) and that could lead to an out of bounds
read.

Fixes: 7ba699c604ab ("[NET_SCHED]: Convert actions from rtnetlink to new netlink API")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/act_ipt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/act_ipt.c
+++ b/net/sched/act_ipt.c
@@ -135,7 +135,7 @@ static int __tcf_ipt_init(struct net *ne
 	}
 
 	td = (struct xt_entry_target *)nla_data(tb[TCA_IPT_TARG]);
-	if (nla_len(tb[TCA_IPT_TARG]) < td->u.target_size) {
+	if (nla_len(tb[TCA_IPT_TARG]) != td->u.target_size) {
 		if (exists)
 			tcf_idr_release(*a, bind);
 		else