[PATCH 3.16 061/254] efi: Move some sysfs files to be read-only by root

Ben Hutchings
2018-02-28T15:20:18Z

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit af97a77bc01ce49a466f9d4c0125479e2e2230b6 upstream.

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
Link: http://lkml.kernel.org/r/20171206095010.24170-2-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.16: drop changes in esrt.c]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -72,8 +72,7 @@ static ssize_t systab_show(struct kobjec
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

--- a/drivers/firmware/efi/runtime-map.c
+++ b/drivers/firmware/efi/runtime-map.c
@@ -67,11 +67,11 @@ static ssize_t map_attr_show(struct kobj
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.
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -82,6 +82,12 @@ 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, \