netdev - [PATCH net-next 02/11] net: sched: cls_u32: make sure that divisor is a power of 2

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Message-Id: <20181007163811.18453-3-jhs@emojatatu.com>
Date:   Sun,  7 Oct 2018 12:38:02 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     davem@...emloft.net
Cc:     jiri@...nulli.us, xiyou.wangcong@...il.com,
        viro@...iv.linux.org.uk, netdev@...r.kernel.org,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: [PATCH net-next 02/11] net: sched: cls_u32: make sure that divisor is a power of 2

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

Tested by modifying iproute2 to to allow
sending a divisor > 255 

Tested-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
---
 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 3357331a80a2..ce55eea448a0 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -994,7 +994,11 @@ 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