Re: [BK PATCH 1/4] remove NGROUPS hard limit (resend)

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> +void
> +qsort(void *a, size_t n, size_t es, cmp_t *cmp)
> +{
> +	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;

A recursive algorithm fed user controlled input that dictates how much
it recurses, in a kernel with a stack limit. Oh and since qsort is
O(N^2) worst case and the user controls the input thats another concern.

> +	if ((r = pb - pa) > es)
> +		qsort(a, r / es, es, cmp);
> +	if ((r = pd - pc) > es) {
> +		/* Iterate rather than recurse to save stack space */


I find it hard to believe that a simple bucket sort wouldnt perform as
well in real life and with a defined time/space, or even something like
shell metzner if you want trivial with good typical behaviour.

Alternatively you could just do a merge pass when a new set of groups is
added.