[PATCH 1/3] efi: move some sysfs files to be read-only by root

Ard Biesheuvel
2017-12-06T09:53:07Z

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

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>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
drivers/firmware/efi/efi.c | 3 +--
drivers/firmware/efi/esrt.c | 15 ++++++---------
drivers/firmware/efi/runtime-map.c | 10 +++++-----
include/linux/sysfs.h | 6 ++++++
4 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index f70febf680c3..c3eefa126e3b 100644
--- a/drivers/firmware/efi/efi.c
+++ b/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

diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
index bd7ed3c1148a..7aae2483fcb9 100644
--- a/drivers/firmware/efi/esrt.c
+++ b/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");
diff --git a/drivers/firmware/efi/runtime-map.c b/drivers/firmware/efi/runtime-map.c
index 8e64b77aeac9..f377609ff141 100644
--- a/drivers/firmware/efi/runtime-map.c
+++ b/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.
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, \
--
2.11.0