linux-kernel - Re: [PATCH v2 1/7] capabilities: introduce CAP_SYS

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Date:   Mon, 16 Dec 2019 09:04:04 -0500
From:   Stephen Smalley <sds@...ho.nsa.gov>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, jani.nikula@...ux.intel.com,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        Alexei Starovoitov <ast@...nel.org>,
        james.bottomley@...senpartnership.com, benh@...nel.crashing.org,
        Casey Schaufler <casey@...aufler-ca.com>, serge@...lyn.com,
        James Morris <jmorris@...ei.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, bgregg@...flix.com,
        Song Liu <songliubraving@...com>, bpf@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 1/7] capabilities: introduce CAP_SYS_PERFMON to kernel
 and user space

On 12/16/19 2:14 AM, Alexey Budankov wrote:
> 
> Introduce CAP_SYS_PERFMON capability devoted to secure system performance
> monitoring and observability operations so that CAP_SYS_PERFMON would assist
> CAP_SYS_ADMIN capability in its governing role for perf_events, i915_perf
> and other performance monitoring and observability subsystems of the kernel.
> 
> CAP_SYS_PERFMON intends to harden system security and integrity during
> system performance monitoring and observability operations by decreasing
> attack surface that is available to CAP_SYS_ADMIN privileged processes.
> 
> CAP_SYS_PERFMON intends to take over CAP_SYS_ADMIN credentials related to
> system performance monitoring and observability operations and balance amount
> of CAP_SYS_ADMIN credentials following with the recommendations provided
> in the capabilities man page [1] for CAP_SYS_ADMIN: "Note: this capability
> is overloaded; see Notes to kernel developers, below."
> 
> [1] http://man7.org/linux/man-pages/man7/capabilities.7.html
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>

Acked-by: Stephen Smalley <sds@...ho.nsa.gov>

> ---
>   include/uapi/linux/capability.h     | 8 +++++++-
>   security/selinux/include/classmap.h | 4 ++--
>   2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
> index 240fdb9a60f6..7d1f8606c3e6 100644
> --- a/include/uapi/linux/capability.h
> +++ b/include/uapi/linux/capability.h
> @@ -366,8 +366,14 @@ struct vfs_ns_cap_data {
>   
>   #define CAP_AUDIT_READ		37
>   
> +/*
> + * Allow system performance and observability privileged operations
> + * using perf_events, i915_perf and other kernel subsystems
> + */
> +
> +#define CAP_SYS_PERFMON		38
>   
> -#define CAP_LAST_CAP         CAP_AUDIT_READ
> +#define CAP_LAST_CAP         CAP_SYS_PERFMON
>   
>   #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
>   
> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
> index 7db24855e12d..bae602c623b0 100644
> --- a/security/selinux/include/classmap.h
> +++ b/security/selinux/include/classmap.h
> @@ -27,9 +27,9 @@
>   	    "audit_control", "setfcap"
>   
>   #define COMMON_CAP2_PERMS  "mac_override", "mac_admin", "syslog", \
> -		"wake_alarm", "block_suspend", "audit_read"
> +		"wake_alarm", "block_suspend", "audit_read", "sys_perfmon"
>   
> -#if CAP_LAST_CAP > CAP_AUDIT_READ
> +#if CAP_LAST_CAP > CAP_SYS_PERFMON
>   #error New capability defined, please update COMMON_CAP2_PERMS.
>   #endif
>   
>