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Message-ID: <c10d7785-1e75-4503-3560-99ab9f845a11@tycho.nsa.gov>
Date: Wed, 18 Dec 2019 14:56:33 -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" <jani.nikula@...ux.intel.com>,
"joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
"rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>,
Alexei Starovoitov <ast@...nel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
"james.bottomley@...senpartnership.com"
<james.bottomley@...senpartnership.com>,
Serge Hallyn <serge@...lyn.com>,
James Morris <jmorris@...ei.org>,
Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>,
Casey Schaufler <casey@...aufler-ca.com>,
Robert Richter <rric@...nel.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>,
Kees Cook <keescook@...omium.org>,
Jann Horn <jannh@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
Song Liu <songliubraving@...com>,
linux-kernel <linux-kernel@...r.kernel.org>,
"linux-security-module@...r.kernel.org"
<linux-security-module@...r.kernel.org>,
"selinux@...r.kernel.org" <selinux@...r.kernel.org>,
"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>,
"linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
linux-arm-kernel@...ts.infradead.org, oprofile-list@...ts.sf.net
Subject: Re: [PATCH v4 1/9] capabilities: introduce CAP_SYS_PERFMON to kernel
and user space
On 12/18/19 4:24 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 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 in accordance with the recommendations
> provided in the man page for CAP_SYS_ADMIN [1]: "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>
Note for selinux developers: we will need to update the
selinux-testsuite tests for perf_event when/if this change lands upstream.
> ---
> include/linux/capability.h | 4 ++++
> include/uapi/linux/capability.h | 8 +++++++-
> security/selinux/include/classmap.h | 4 ++--
> 3 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/capability.h b/include/linux/capability.h
> index ecce0f43c73a..883c879baa4b 100644
> --- a/include/linux/capability.h
> +++ b/include/linux/capability.h
> @@ -251,6 +251,10 @@ extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct
> extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
> extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
> extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
> +static inline bool perfmon_capable(void)
> +{
> + return capable(CAP_SYS_PERFMON) || capable(CAP_SYS_ADMIN);
> +}
>
> /* audit system wants to get cap info from files as well */
> extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
> diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
> index 240fdb9a60f6..98e03cc76c7c 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
>
>
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