net_sched: fix an OOB access in cls_tcindex

net_sched: fix an OOB access in cls_tcindex

As Eric noticed, tcindex_alloc_perfect_hash() uses cp->hash
to compute the size of memory allocation, but cp->hash is
set again after the allocation, this caused an out-of-bound
access.

So we have to move all cp->hash initialization and computation
before the memory allocation. Move cp->mask and cp->shift together
as cp->hash may need them for computation too.

Reported-and-tested-by: [email protected]
Fixes: 331b72922c5f ("net: sched: RCU cls_tcindex")
Cc: Eric Dumazet <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: Jamal Hadi Salim <[email protected]>
Cc: Jiri Pirko <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Signed-off-by: Cong Wang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>