net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()

In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()

Commit 38a6f0865796 ("net: sched: support hash selecting tx queue")

added SKBEDIT_F_TXQ_SKBHASH support. The inclusive range size is

computed as:

mapping_mod = queue_mapping_max - queue_mapping + 1;

The range size can be 65536 when the requested range covers all possible

u16 queue IDs (e.g. queue_mapping=0 and queue_mapping_max=U16_MAX).

That value cannot be represented in a u16 and previously wrapped to 0,

so tcf_skbedit_hash() could trigger a divide-by-zero:

queue_mapping += skb_get_hash(skb) % params->mapping_mod;

Compute mapping_mod in a wider type and reject ranges larger than U16_MAX

to prevent params->mapping_mod from becoming 0 and avoid the crash.