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: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ard 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.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index e32dfe098e82..40839c02d28c 100644
--- a/include/linux/sysfs.h
+++ b/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,					\