[PATCH 3.16 285/328] net: sched: act_ipt: check for underflow in __tcf_ipt_init()

Ben Hutchings
2018-12-09T22:02:06Z

From: Dan Carpenter <dan.carpenter@oracle.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@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.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)