linux-kernel - Re: [PATCH v2 18/18] perf: arm_spe: Disallow userspace profiling when arm_kernel_unmapped_at

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20171201162639.GD19419@codeaurora.org>
Date:   Fri, 1 Dec 2017 08:26:39 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Will Deacon <will.deacon@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, mark.rutland@....com,
        ard.biesheuvel@...aro.org, dave.hansen@...ux.intel.com,
        keescook@...omium.org, msalter@...hat.com, labbott@...hat.com,
        tglx@...utronix.de
Subject: Re: [PATCH v2 18/18] perf: arm_spe: Disallow userspace profiling
 when arm_kernel_unmapped_at_el0()

On 11/30, Will Deacon wrote:
> When running with the kernel unmapped whilst at EL0, the virtually-addressed
> SPE buffer is also unmapped, which can lead to buffer faults if userspace
> profiling is enabled.
> 
> This patch prohibits SPE profiling of userspace when
> arm_kernel_unmapped_at_el0().
> 
> Signed-off-by: Will Deacon <will.deacon@....com>
> ---
>  drivers/perf/arm_spe_pmu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> index 8ce262fc2561..c028db8973a4 100644
> --- a/drivers/perf/arm_spe_pmu.c
> +++ b/drivers/perf/arm_spe_pmu.c
> @@ -675,6 +675,13 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
>  		return -EOPNOTSUPP;
>  
>  	/*
> +	 * If kernelspace is unmapped when running at EL0, then the SPE
> +	 * buffer will fault and prematurely terminate the AUX session.
> +	 */
> +	if (arm64_kernel_unmapped_at_el0() && !attr->exclude_user)
> +		dev_warn_once(&spe_pmu->pdev->dev, "unable to write to profiling buffer from EL0. Try passing \"kaiser=off\" on the kernel command line");

Missing newline on that print?

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project