efi: Move some sysfs files to be read-only by root

Thanks to the scripts/leaking_addresses.pl script, it was found that
some EFI values should not be readable by non-root users.

So make them root-only, and to do that, add a __ATTR_RO_MODE() macro to
make this easier, and use it in other places at the same time.
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: NDave Young <dyoung@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: stable <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20171206095010.24170-2-ard.biesheuvel@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

drivers/firmware/efi/efi.c

@@ -143,8 +143,7 @@ static ssize_t systab_show(struct kobject *kobj,
 	return str - buf;
 }
 
-static struct kobj_attribute efi_attr_systab =
-			__ATTR(systab, 0400, systab_show, NULL);
+static struct kobj_attribute efi_attr_systab = __ATTR_RO_MODE(systab, 0400);
 
 #define EFI_FIELD(var) efi.var
 

drivers/firmware/efi/esrt.c

@@ -106,7 +106,7 @@ static const struct sysfs_ops esre_attr_ops = {
 };
 
 /* Generic ESRT Entry ("ESRE") support. */
-static ssize_t esre_fw_class_show(struct esre_entry *entry, char *buf)
+static ssize_t fw_class_show(struct esre_entry *entry, char *buf)
 {
 	char *str = buf;
 
@@ -117,18 +117,16 @@ static ssize_t esre_fw_class_show(struct esre_entry *entry, char *buf)
 	return str - buf;
 }
 
-static struct esre_attribute esre_fw_class = __ATTR(fw_class, 0400,
-	esre_fw_class_show, NULL);
+static struct esre_attribute esre_fw_class = __ATTR_RO_MODE(fw_class, 0400);
 
 #define esre_attr_decl(name, size, fmt) \
-static ssize_t esre_##name##_show(struct esre_entry *entry, char *buf) \
+static ssize_t name##_show(struct esre_entry *entry, char *buf) \
 { \
 	return sprintf(buf, fmt "\n", \
 		       le##size##_to_cpu(entry->esre.esre1->name)); \
 } \
 \
-static struct esre_attribute esre_##name = __ATTR(name, 0400, \
-	esre_##name##_show, NULL)
+static struct esre_attribute esre_##name = __ATTR_RO_MODE(name, 0400)
 
 esre_attr_decl(fw_type, 32, "%u");
 esre_attr_decl(fw_version, 32, "%u");
@@ -193,14 +191,13 @@ static int esre_create_sysfs_entry(void *esre, int entry_num)
 
 /* support for displaying ESRT fields at the top level */
 #define esrt_attr_decl(name, size, fmt) \
-static ssize_t esrt_##name##_show(struct kobject *kobj, \
+static ssize_t name##_show(struct kobject *kobj, \
 				  struct kobj_attribute *attr, char *buf)\
 { \
 	return sprintf(buf, fmt "\n", le##size##_to_cpu(esrt->name)); \
 } \
 \
-static struct kobj_attribute esrt_##name = __ATTR(name, 0400, \
-	esrt_##name##_show, NULL)
+static struct kobj_attribute esrt_##name = __ATTR_RO_MODE(name, 0400)
 
 esrt_attr_decl(fw_resource_count, 32, "%u");
 esrt_attr_decl(fw_resource_count_max, 32, "%u");

drivers/firmware/efi/runtime-map.c

@@ -63,11 +63,11 @@ static ssize_t map_attr_show(struct kobject *kobj, struct attribute *attr,
 	return map_attr->show(entry, buf);
 }
 
-static struct map_attribute map_type_attr = __ATTR_RO(type);
-static struct map_attribute map_phys_addr_attr   = __ATTR_RO(phys_addr);
-static struct map_attribute map_virt_addr_attr  = __ATTR_RO(virt_addr);
-static struct map_attribute map_num_pages_attr  = __ATTR_RO(num_pages);
-static struct map_attribute map_attribute_attr  = __ATTR_RO(attribute);
+static struct map_attribute map_type_attr = __ATTR_RO_MODE(type, 0400);
+static struct map_attribute map_phys_addr_attr = __ATTR_RO_MODE(phys_addr, 0400);
+static struct map_attribute map_virt_addr_attr = __ATTR_RO_MODE(virt_addr, 0400);
+static struct map_attribute map_num_pages_attr = __ATTR_RO_MODE(num_pages, 0400);
+static struct map_attribute map_attribute_attr = __ATTR_RO_MODE(attribute, 0400);
 
 /*
  * These are default attributes that are added for every memmap entry.

include/linux/sysfs.h

@@ -117,6 +117,12 @@ struct attribute_group {
 	.show	= _name##_show,						\
 }
 
+#define __ATTR_RO_MODE(_name, _mode) {					\
+	.attr	= { .name = __stringify(_name),				\
+		    .mode = VERIFY_OCTAL_PERMISSIONS(_mode) },		\
+	.show	= _name##_show,						\
+}
+
 #define __ATTR_WO(_name) {						\
 	.attr	= { .name = __stringify(_name), .mode = S_IWUSR },	\
 	.store	= _name##_store,					\