linux-kernel - [PATCH 08/12] driver-core: Introduce DEVICE_ATTR_ADMIN

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Message-ID: <159312906372.1850128.11611897078988158727.stgit@dwillia2-desk3.amr.corp.intel.com>
Date:   Thu, 25 Jun 2020 16:51:03 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     linux-nvdimm@...ts.01.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        vishal.l.verma@...el.com, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 08/12] driver-core: Introduce DEVICE_ATTR_ADMIN_{RO,RW}

A common pattern for using plain DEVICE_ATTR() instead of
DEVICE_ATTR_RO() and DEVICE_ATTR_RW() is for attributes that want to
limit read to only root.  I.e. many users of DEVICE_ATTR() are
specifying 0400 or 0600 for permissions.

Given the expectation that CAP_SYS_ADMIN is needed to access these
sensitive attributes and an explicit helper with the _ADMIN_ identifier
for DEVICE_ATTR_ADMIN_{RO,RW}.

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 include/linux/device.h |    4 ++++
 include/linux/sysfs.h  |    7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/include/linux/device.h b/include/linux/device.h
index 15460a5ac024..d7c2570368fa 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -128,8 +128,12 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,
 		__ATTR_PREALLOC(_name, _mode, _show, _store)
 #define DEVICE_ATTR_RW(_name) \
 	struct device_attribute dev_attr_##_name = __ATTR_RW(_name)
+#define DEVICE_ATTR_ADMIN_RW(_name) \
+	struct device_attribute dev_attr_##_name = __ATTR_RW_MODE(_name, 0600)
 #define DEVICE_ATTR_RO(_name) \
 	struct device_attribute dev_attr_##_name = __ATTR_RO(_name)
+#define DEVICE_ATTR_ADMIN_RO(_name) \
+	struct device_attribute dev_attr_##_name = __ATTR_RO_MODE(_name, 0400)
 #define DEVICE_ATTR_WO(_name) \
 	struct device_attribute dev_attr_##_name = __ATTR_WO(_name)
 #define DEVICE_ULONG_ATTR(_name, _mode, _var) \
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 86067dbe7745..34e84122f635 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -123,6 +123,13 @@ struct attribute_group {
 	.show	= _name##_show,						\
 }
 
+#define __ATTR_RW_MODE(_name, _mode) {					\
+	.attr	= { .name = __stringify(_name),				\
+		    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
+	.show	= _name##_show,						\
+	.store	= _name##_store,					\
+}
+
 #define __ATTR_WO(_name) {						\
 	.attr	= { .name = __stringify(_name), .mode = 0200 },		\
 	.store	= _name##_store,					\