linux-kernel - [PATCH 3.16 285/328] net: sched: act_ipt: check for underflow in __tcf_ipt

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Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Dan Carpenter" <dan.carpenter@...cle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 285/328] net: sched: act_ipt: check for underflow in
 __tcf_ipt_init()

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

commit aeadd93f2b0a609f603ac33e574b97a9832d1b90 upstream.

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@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -107,7 +107,7 @@ static int tcf_ipt_init(struct net *net,
 		return -EINVAL;
 
 	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)
 		return -EINVAL;
 
 	if (tb[TCA_IPT_INDEX] != NULL)