Re: [PATCH 1/2] sched_ext: Deny SCX kfuncs to non-SCX struct_ops programs

[Tejun Heo <tj@kernel.org>]

Hello,

A few things:

scx_kfunc_set_idle (ext_idle.c) isn't covered by the patch. Its kfuncs
(scx_bpf_cpu_node(), scx_bpf_get_idle_cpumask(), scx_bpf_pick_idle_cpu()
etc.) also call scx_prog_sched(aux) and hit the same OOB pattern on
non-SCX struct_ops programs. Please add an in_idle check in the filter
and treat it the same as in_any.

Separately, please also set .filter on scx_kfunc_set_idle itself. In
practice, the BPF core dedups filters per hook in
btf_populate_kfunc_set(), so the filter is already invoked for idle
kfuncs via the other sets' registrations on the same hook. But it's
confusing to read the code without setting .filter on every set.

The following line is too long - please break and indent (it gets
longer still once in_idle is added):

> +	if (!(in_unlocked || in_select_cpu || in_enqueue || in_dispatch || in_cpu_release || in_any))

Once idle is covered, every SCX kfunc set ends up in this "context-
sensitive" list. At that point "context-sensitive" no longer
distinguishes anything - it just means "SCX kfuncs". Please update the
function-level comment and the two inline comments ("Not a context-
sensitive kfunc - allow." and "Non-SCX struct_ops: context-sensitive
kfuncs are not permitted.") to drop the term and talk about SCX kfuncs
directly.

Thanks.

--
tejun