On Tue, Oct 20, 2015 at 10:13:15PM +0300, Pantelis Antoniou wrote: > A throw once master enable switch to protect against any > further overlay applications if the administrator desires so. > > Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> > --- > drivers/of/overlay.c | 43 ++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 42 insertions(+), 1 deletion(-) > > diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c > index 12c3e47..067404e 100644 > --- a/drivers/of/overlay.c > +++ b/drivers/of/overlay.c > @@ -21,6 +21,7 @@ > #include <linux/err.h> > #include <linux/idr.h> > #include <linux/sysfs.h> > +#include <linux/atomic.h> > > #include "of_private.h" > > @@ -55,8 +56,12 @@ struct of_overlay { > struct kobject kobj; > }; > > +/* master enable switch; once set to 0 can't be re-enabled */ > +static atomic_t ov_enable = ATOMIC_INIT(1); > + > static int of_overlay_apply_one(struct of_overlay *ov, > struct device_node *target, const struct device_node *overlay); > +static int overlay_removal_is_ok(struct of_overlay *ov); > > static int of_overlay_apply_single_property(struct of_overlay *ov, > struct device_node *target, struct property *prop) > @@ -339,6 +344,35 @@ void of_overlay_release(struct kobject *kobj) > kfree(ov); > } > > +static ssize_t enable_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return snprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&ov_enable)); > +} > + > +static ssize_t enable_store(struct kobject *kobj, > + struct kobj_attribute *attr, const char *buf, size_t count) > +{ > + int ret; > + bool new_enable; > + > + ret = strtobool(buf, &new_enable); > + if (ret != 0) > + return ret; > + /* if we've disabled it, no going back */ > + if (atomic_read(&ov_enable) == 0) > + return -EPERM; > + atomic_set(&ov_enable, (int)new_enable); > + return count; > +} > + > +static struct kobj_attribute enable_attr = __ATTR_RW(enable); > + > +static const struct attribute *overlay_global_attrs[] = { > + &enable_attr.attr, > + NULL > +}; > + > static struct kobj_type of_overlay_ktype = { > .release = of_overlay_release, > }; > @@ -360,6 +394,10 @@ int of_overlay_create(struct device_node *tree) > struct of_overlay *ov; > int err, id; > > + /* administratively disabled */ > + if (!atomic_read(&ov_enable)) > + return -EPERM; > + > /* allocate the overlay structure */ > ov = kzalloc(sizeof(*ov), GFP_KERNEL); > if (ov == NULL) > @@ -594,5 +632,8 @@ int of_overlay_init(void) > if (!ov_kset) > return -ENOMEM; > > - return 0; > + rc = sysfs_create_files(&ov_kset->kobj, overlay_global_attrs); > + WARN(rc, "%s: error adding global attributes\n", __func__); > + > + return rc; > } Shouldn't this also be allowed to be overridden as a boot and build time parameter to prevent any races on systems that don't want this? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html