CVE-2024-57947: Missing Release of Memory after Effective Lifetime

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

netfilter: nf_set_pipapo: fix initial map fill

The initial buffer has to be inited to all-ones, but it must restrict it to the size of the first field, not the total field size.

After each round in the map search step, the result and the fill map are swapped, so if we have a set where f->bsize of the first element is smaller than m->bsize_max, those one-bits are leaked into future rounds result map.

This makes pipapo find an incorrect matching results for sets where first field size is not the largest.

Followup patch adds a test case to nft_concat_range.sh selftest script.

Thanks to Stefano Brivio for pointing out that we need to zero out the remainder explicitly, only correcting memset() argument isn't enough.