[PATCH 06/44] kernel/ksysfs.c: expose file_caps_enabled in sysfs

Greg Kroah-Hartman
2011-05-20T00:21:05Z

From: Ludwig Nussel <ludwig.nussel@suse.de>

A kernel booted with no_file_caps allows to install fscaps on a binary
but doesn't actually honor the fscaps when running the binary. Userspace
currently has no sane way to determine whether installing fscaps
actually has any effect. Since parsing /proc/cmdline is fragile this
patch exposes the current setting (1 or 0) via /sys/kernel/fscaps

Signed-off-by: Ludwig Nussel <ludwig.nussel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
Documentation/ABI/testing/sysfs-kernel-fscaps | 8 ++++++++
kernel/ksysfs.c | 10 ++++++++++
2 files changed, 18 insertions(+), 0 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-fscaps

diff --git a/Documentation/ABI/testing/sysfs-kernel-fscaps b/Documentation/ABI/testing/sysfs-kernel-fscaps
new file mode 100644
index 0000000..50a3033
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-fscaps
@@ -0,0 +1,8 @@
+What: /sys/kernel/fscaps
+Date: February 2011
+KernelVersion: 2.6.38
+Contact: Ludwig Nussel <ludwig.nussel@suse.de>
+Description
+ Shows whether file system capabilities are honored
+ when executing a binary
+
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 0b624e7..3b053c0 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -16,6 +16,7 @@
#include <linux/kexec.h>
#include <linux/profile.h>
#include <linux/sched.h>
+#include <linux/capability.h>

#define KERNEL_ATTR_RO(_name) \
static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
@@ -131,6 +132,14 @@ KERNEL_ATTR_RO(vmcoreinfo);

#endif /* CONFIG_KEXEC */

+/* whether file capabilities are enabled */
+static ssize_t fscaps_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", file_caps_enabled);
+}
+KERNEL_ATTR_RO(fscaps);
+
/*
* Make /sys/kernel/notes give the raw contents of our kernel .notes section.
*/
@@ -158,6 +167,7 @@ struct kobject *kernel_kobj;
EXPORT_SYMBOL_GPL(kernel_kobj);

static struct attribute * kernel_attrs[] = {
+ &fscaps_attr.attr,
#if defined(CONFIG_HOTPLUG)
&uevent_seqnum_attr.attr,
&uevent_helper_attr.attr,
--
1.7.4.2