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

From: "Lubashev, Igor" <ilubashe@akamai.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Alexey Budankov <alexey.budankov@linux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>, Leo Yan <leo.yan@linaro.org>,
	Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks
Date: Tue, 27 Aug 2019 01:58:35 +0000	[thread overview]
Message-ID: <c647400a6c164bdab2cadfb7c0f1b519@usma1ex-dag1mb6.msg.corp.akamai.com> (raw)
In-Reply-To: <20190820171342.GD3929@kernel.org>

On Tue, August 20, 2019 at 1:14 PM Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> 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: https://lkml.kernel.org/lkml/1566869956-7154-1-git-send-email-ilubashe@akamai.com/ 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

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