linux-kernel - [PATCH v1 1/3] capabilities: introduce CAP_SYS

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Message-ID: <4ebe4d05-85c3-20dc-89a4-ed8f052d586e@linux.intel.com>
Date:   Thu, 5 Dec 2019 19:19:51 +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>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        elena.reshetova@...el.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Stephane Eranian <eranian@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 1/3] capabilities: introduce CAP_SYS_PERFMON to kernel and
 user space


Introduce CAP_SYS_PERFMON capability dedicated to secure performance
monitoring activity so that CAP_SYS_PERFMON would assist CAP_SYS_ADMIN
capability in its governing role for perf_events based performance
monitoring of a system.

CAP_SYS_PERFMON aims to harden system security and integrity during
performance monitoring by decreasing attack surface that is available
to CAP_SYS_ADMIN privileged processes.

CAP_SYS_PERFMON aims to take over CAP_SYS_ADMIN credentials related to
performance monitoring functionality of perf_events and balance amount of
CAP_SYS_ADMIN credentials in accordance with the recommendations provided in
the man page for CAP_SYS_ADMIN [3]: "Note: this capability is overloaded;
see Notes to kernel developers, below."

Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
---
 include/uapi/linux/capability.h     | 10 +++++++++-
 security/selinux/include/classmap.h |  4 ++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index 240fdb9a60f6..c9514f034be1 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -366,8 +366,16 @@ struct vfs_ns_cap_data {
 
 #define CAP_AUDIT_READ		37
 
+/*
+ * Allow usage of perf_event_open() syscall (perf_events subsystem):
+ * http://man7.org/linux/man-pages/man2/perf_event_open.2.html
+ * beyond the scope permitted by perf_event_paranoid kernel setting.
+ * See Documentation/admin-guide/perf-security.rst for more information.
+ */
+
+#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