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Date: Tue, 2 Aug 2016 11:55:46 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Jeff Vander Stoep <jeffv@...gle.com>
Cc: kernel-hardening@...ts.openwall.com, mingo@...hat.com, acme@...nel.org,
alexander.shishkin@...ux.intel.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] security, perf: Add config option to restrict
perf_event_open
On Wed, Jul 27, 2016 at 07:46:23AM -0700, Jeff Vander Stoep wrote:
> +++ b/kernel/events/core.c
> @@ -355,7 +355,11 @@ static struct srcu_struct pmus_srcu;
> * 2 - disallow kernel profiling for unpriv
> * 3 - disallow all unpriv perf event use
> */
> +#ifdef CONFIG_SECURITY_PERF_EVENTS_RESTRICT
> +int sysctl_perf_event_paranoid __read_mostly = 3;
> +#else
> int sysctl_perf_event_paranoid __read_mostly = 2;
> +#endif
>
> /* Minimum for 512 kiB + 1 user control page */
> int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
> diff --git a/security/Kconfig b/security/Kconfig
> index df28f2b..2a93551 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -18,6 +18,15 @@ config SECURITY_DMESG_RESTRICT
>
> If you are unsure how to answer this question, answer N.
>
> +config SECURITY_PERF_EVENTS_RESTRICT
> + bool "Restrict unprivileged use of performance events"
> + depends on PERF_EVENTS
> + help
> + If you say Y here, the kernel.perf_event_paranoid sysctl
> + will be set to 3 by default, and no unprivileged use of the
> + perf_event_open syscall will be permitted unless it is
> + changed.
NAK.
Apart from the fact that I hate the 3 thing this is not how you do
default CONFIG knobs for !bool state variables.
Use an "int" config not a "bool" config and allow all options to be
default.
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