RE: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks

From: Lubashev, Igor
Date: Mon Aug 26 2019 - 21:59:00 EST

On Tue, August 20, 2019 at 1:14 PM Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> wrote:
> > Arnaldo, once we decide what the right fix is, I am happy to post the
> update (options 1, 1+2) as a patch series.
> I think you should get the checks for ref_reloc_sym in place so as to make the
> code overall more robust, and also go on continuing to make the checks in
> tools/perf/ to match what is checked on the other side of the mirror, i.e. by
> the kernel, so from a quick read, please put first the robustness patches
> (check ref_reloc_sym) do your other suggestions and update the warnings,
> then refresh the two patches that still are not in my perf/core branch:
> [acme@quaco perf]$ git rebase perf/core
> First, rewinding head to replay your work on top of it...
> Applying: perf tools: Use CAP_SYS_ADMIN with perf_event_paranoid checks
> Applying: perf symbols: Use CAP_SYSLOG with kptr_restrict checks
> [acme@quaco perf]$
> I've pushed out perf/cap, so you can go from there as it is rebased on my
> current perf/core.
> Then test all these cases: with/without libcap, with euid==0 and different
> than zero, with capabilities, etc, patch by patch so that we don't break
> bisection nor regress,

All done. I've posted the update as a new follow-up series: rebased on your perf/core.

I've tested 336 permutations (see the new cover). In particular, I was able to reproduce the crash on perf/cap and confirm that no permutation can cause such crashes for any of the patches in the series.

> Thanks and keep up the good work!
> - Arnaldo

- Igor