Subject: [PATCH v4 1/9] capabilities: introduce CAP_SYS_PERFMON to kernel and user space

From: Alexey Budankov <[email-masked]>
Date: Wed, 18 Dec 2019 12:24:28 +0300

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 <[email-masked]>
---
 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
 
-- 
2.20.1