From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752812AbbJTVGM (ORCPT ); Tue, 20 Oct 2015 17:06:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42138 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751274AbbJTVGK (ORCPT ); Tue, 20 Oct 2015 17:06:10 -0400 Date: Tue, 20 Oct 2015 14:06:09 -0700 From: Greg Kroah-Hartman To: Pantelis Antoniou Cc: Rob Herring , Frank Rowand , Matt Porter , Koen Kooi , Guenter Roeck , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Pantelis Antoniou Subject: Re: [PATCH v6 2/4] of: overlay: global sysfs enable attribute Message-ID: <20151020210609.GB28724@kroah.com> References: <1445368397-8732-1-git-send-email-pantelis.antoniou@konsulko.com> <1445368397-8732-3-git-send-email-pantelis.antoniou@konsulko.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1445368397-8732-3-git-send-email-pantelis.antoniou@konsulko.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 > #include > #include > +#include > > #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