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


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