From: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon, 8 Oct 2018 06:22:35 -0400
Subject: net: sched: cls_u32: make sure that divisor is a power of 2
Patch-mainline: v4.20-rc1
Git-commit: 2f0c982df7b146f9aa695ede91b48392ab4c3217
References: bsc#1109837

Tested by modifying iproute2 to allow sending a divisor > 255

Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/cls_u32.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -995,7 +995,11 @@ static int u32_change(struct net *net, s
 	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;
 		}