net: sched: cls_u32: make sure that divisor is a power of 2

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>

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 3357331..ce55eea 100644 (file)
--- 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;
                }