[PATCH 1/1] lib: sbi_pmu: check for index overflows

[Vivian Wang]

Good catch on the untrusted value but I think this is already checked?

	/* Do a basic sanity check of counter base & mask */
	if ((cidx_base + sbi_fls(cidx_mask)) >= total_ctrs)
		return SBI_EINVAL;

But I suppose this could overflow, in which case probably just add this?

	if (cidx_base >= total_ctrs || ...)

total_ctrs is small anyway (there shouldn't a billion counters right?)
so this should be fine. If we do that we probably should modify the
checks in sbi_pmu_ctr_{start,stop} as well for consistency.

I also checked if the IPI stuff have this problem but I'm pretty sure
the hart indices are range-checked individually. It's probably still a
good idea to add a "base and mask is sane" check there.

Thanks,
Vivian aka "dram"