netdev - [PATCH 3/7] make sure that divisor is a power of 2

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Message-Id: <20180905190414.5477-3-viro@ZenIV.linux.org.uk>
Date:   Wed,  5 Sep 2018 20:04:10 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     netdev@...r.kernel.org
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: [PATCH 3/7] make sure that divisor is a power of 2

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 net/sched/cls_u32.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 9ea5f2be907b..5816288810cc 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -995,7 +995,11 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 	if (tb[TCA_U32_DIVISOR]) {
 		unsigned int divisor = nla_get_u32(tb[TCA_U32_DIVISOR]);
 
-		if (--divisor > 0x100) {
+		if (!is_power_of_2(divisor)) {
+			NL_SET_ERR_MSG_MOD(extack, "Divisor is not a power of 2");
+			return -EINVAL;
+		}
+		if (divisor-- > 0x100) {
 			NL_SET_ERR_MSG_MOD(extack, "Exceeded maximum 256 hash buckets");
 			return -EINVAL;
 		}
-- 
2.11.0