linux-kernel - [PATCH v3 1/7] capabilities: introduce CAP_SYS

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Message-ID: <bd8adfde-f562-0e56-75aa-371c5354f350@linux.intel.com>
Date:   Mon, 16 Dec 2019 22:58:02 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     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>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>,
        Casey Schaufler <casey@...aufler-ca.com>
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>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org,
        Brendan Gregg <bgregg@...flix.com>, songliubraving@...com,
        "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>
Subject: [PATCH v3 1/7] capabilities: introduce CAP_SYS_PERFMON to kernel and
 user space


Introduce CAP_SYS_PERFMON capability devoted to secure system performance
monitoring and observability 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 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 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>
---
 include/linux/capability.h          | 1 +
 include/uapi/linux/capability.h     | 8 +++++++-
 security/selinux/include/classmap.h | 4 ++--
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index ecce0f43c73a..6342502c4c2a 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -251,6 +251,7 @@ 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);
+#define perfmon_capable() (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
 
-- 
2.20.1