Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751480AbaKYOui (ORCPT ); Tue, 25 Nov 2014 09:50:38 -0500 Received: from li42-95.members.linode.com ([209.123.162.95]:37150 "EHLO li42-95.members.linode.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751270AbaKYOuc convert rfc822-to-8bit (ORCPT ); Tue, 25 Nov 2014 09:50:32 -0500 Subject: Re: [PATCH v8 3/8] OF: DT-Overlay configfs interface (v2) Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\)) Content-Type: text/plain; charset=utf-8 From: Pantelis Antoniou In-Reply-To: <20141125102844.79BAEC44089@trevor.secretlab.ca> Date: Tue, 25 Nov 2014 16:50:15 +0200 Cc: Rob Herring , Stephen Warren , Matt Porter , Koen Kooi , Greg Kroah-Hartman , Alison Chaiken , Dinh Nguyen , Jan Lubbe , Alexander Sverdlin , Michael Stickel , Guenter Roeck , Dirk Behme , Alan Tull , Sascha Hauer , Michael Bohan , Ionut Nicu , Michal Simek , Matt Ranostay , Joel Becker , devicetree@vger.kernel.org, Wolfram Sang , linux-i2c@vger.kernel.org, Mark Brown , linux-spi@vger.kernel.org, linux-kernel , Pete Popov , Dan Malek , Georgi Vlaev Content-Transfer-Encoding: 8BIT Message-Id: <773D4828-4530-46E7-8786-1DBA490C36EB@antoniou-consulting.com> References: <1414528565-10907-1-git-send-email-pantelis.antoniou@konsulko.com> <1414528565-10907-4-git-send-email-pantelis.antoniou@konsulko.com> <20141125102844.79BAEC44089@trevor.secretlab.ca> To: Grant Likely X-Mailer: Apple Mail (2.1993) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Grant, > On Nov 25, 2014, at 12:28 , Grant Likely wrote: > > Hi Pantelis, > > Comments below... > > On Tue, 28 Oct 2014 22:36:00 +0200 > , Pantelis Antoniou > wrote: >> Add a runtime interface to using configfs for generic device tree overlay >> usage. >> >> A device-tree configfs entry is created in /config/device-tree/overlays >> >> * To create an overlay you mkdir the directory: >> >> # mkdir /config/device-tree/overlays/foo >> >> * Either you echo the overlay firmware file to the path property file. >> >> # echo foo.dtbo >/config/device-tree/overlays/foo/path >> >> * Or you cat the contents of the overlay to the dtbo file >> >> # cat foo.dtbo >/config/device-tree/overlays/foo/dtbo >> >> The overlay file will be applied. >> >> To remove it simply rmdir the directory. >> >> # rmdir /config/device-tree/overlays/foo > > The above is documentation on how to use it, but it isn't a good commit > message. The above should be moved into a documentation file (if it > isn't already and I've missed it) and the commit message should give > detail about what was needed, what was changed to make it happen, and > what the result of the new code is. > Hmm, okie dokie. >> >> Changes since v1: >> * of_resolve() -> of_resolve_phandles(). >> >> Signed-off-by: Pantelis Antoniou >> --- >> drivers/of/Kconfig | 7 ++ >> drivers/of/Makefile | 1 + >> drivers/of/configfs.c | 340 ++++++++++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 348 insertions(+) >> create mode 100644 drivers/of/configfs.c >> >> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig >> index aa315c4..d59ba40 100644 >> --- a/drivers/of/Kconfig >> +++ b/drivers/of/Kconfig >> @@ -90,4 +90,11 @@ config OF_OVERLAY >> select OF_DEVICE >> select OF_RESOLVE >> >> +config OF_CONFIGFS >> + bool "OpenFirmware Overlay ConfigFS interface" > > Despite all the APIs being prefixed with OpenFirmware, this isn't an > OpenFirmware interface, it is a device tree interface. > OK, so device tree config fs interface? >> + select CONFIGFS_FS >> + select OF_OVERLAY >> + help >> + Enable a simple user-space driver DT overlay interface. >> + >> endmenu # OF >> diff --git a/drivers/of/Makefile b/drivers/of/Makefile >> index 1bfe462..6d12949 100644 >> --- a/drivers/of/Makefile >> +++ b/drivers/of/Makefile >> @@ -15,6 +15,7 @@ obj-$(CONFIG_OF_MTD) += of_mtd.o >> obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o >> obj-$(CONFIG_OF_RESOLVE) += resolver.o >> obj-$(CONFIG_OF_OVERLAY) += overlay.o >> +obj-$(CONFIG_OF_CONFIGFS) += configfs.o > > Tip: Insert lines in the middle of the block, roughly alphabetically > sorted. It cuts down on merge conflicts that way. > k >> >> CFLAGS_fdt.o = -I$(src)/../../scripts/dtc/libfdt >> CFLAGS_fdt_address.o = -I$(src)/../../scripts/dtc/libfdt >> diff --git a/drivers/of/configfs.c b/drivers/of/configfs.c >> new file mode 100644 >> index 0000000..932f572 >> --- /dev/null >> +++ b/drivers/of/configfs.c >> @@ -0,0 +1,340 @@ >> +/* >> + * Configfs entries for device-tree >> + * >> + * Copyright (C) 2013 - Pantelis Antoniou >> + * >> + * This program is free software; you can redistribute it and/or >> + * modify it under the terms of the GNU General Public License >> + * as published by the Free Software Foundation; either version >> + * 2 of the License, or (at your option) any later version. >> + */ >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +#include "of_private.h" >> + >> +#ifdef CONFIG_OF_OVERLAY > > ??? > > This file shouldn't even be compiled if CONFIG_OF_OVERLAY isn't > selected. Why is this here? > Err, good question. >> + >> +struct cfs_overlay_item { >> + struct config_item item; >> + >> + char path[PATH_MAX]; >> + >> + const struct firmware *fw; >> + struct device_node *overlay; >> + int ov_id; >> + >> + void *dtbo; >> + int dtbo_size; >> +}; >> + >> +static int create_overlay(struct cfs_overlay_item *overlay, void *blob) >> +{ >> + int err; >> + >> + /* unflatten the tree */ >> + of_fdt_unflatten_tree((void *)blob, &overlay->overlay); > > blob is already void* > ok >> + if (overlay->overlay == NULL) { >> + pr_err("%s: failed to unflatten tree\n", __func__); >> + err = -EINVAL; >> + goto out_err; >> + } >> + pr_debug("%s: unflattened OK\n", __func__); >> + >> + /* mark it as detached */ >> + of_node_set_flag(overlay->overlay, OF_DETACHED); >> + >> + /* perform resolution */ >> + err = of_resolve_phandles(overlay->overlay); >> + if (err != 0) { >> + pr_err("%s: Failed to resolve tree\n", __func__); >> + goto out_err; >> + } >> + pr_debug("%s: resolved OK\n", __func__); >> + >> + err = of_overlay_create(overlay->overlay); >> + if (err < 0) { >> + pr_err("%s: Failed to create overlay (err=%d)\n", >> + __func__, err); >> + goto out_err; >> + } >> + overlay->ov_id = err; >> + >> +out_err: >> + return err; >> +} >> + >> +static inline struct cfs_overlay_item *to_cfs_overlay_item( >> + struct config_item *item) >> +{ >> + return item ? container_of(item, struct cfs_overlay_item, item) : NULL; >> +} >> + >> +CONFIGFS_ATTR_STRUCT(cfs_overlay_item); >> +#define CFS_OVERLAY_ITEM_ATTR(_name, _mode, _show, _store) \ >> +struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \ >> + __CONFIGFS_ATTR(_name, _mode, _show, _store) >> +#define CFS_OVERLAY_ITEM_ATTR_RO(_name, _show) \ >> +struct cfs_overlay_item_attribute cfs_overlay_item_attr_##_name = \ >> + __CONFIGFS_ATTR_RO(_name, _show) >> + >> +CONFIGFS_BIN_ATTR_STRUCT(cfs_overlay_item); >> +#define CFS_OVERLAY_ITEM_BIN_ATTR(_name, _mode, _read, _write, _priv, _max) \ >> +struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = \ >> + __CONFIGFS_BIN_ATTR(_name, _mode, _read, _write, _priv, _max) >> +#define CFS_OVERLAY_ITEM_BIN_ATTR_RO(_name, _read, _priv, _max) \ >> +struct cfs_overlay_item_bin_attribute cfs_overlay_item_bin_attr_##_name = \ >> + __CONFIGFS_BIN_ATTR_RO(_name, _read, _priv, _max) >> + >> +static ssize_t cfs_overlay_item_path_show(struct cfs_overlay_item *overlay, >> + char *page) >> +{ >> + return sprintf(page, "%s\n", overlay->path); >> +} >> + >> +static ssize_t cfs_overlay_item_path_store(struct cfs_overlay_item *overlay, >> + const char *page, size_t count) >> +{ >> + const char *p = page; >> + char *s; >> + int err; >> + >> + /* if it's set do not allow changes */ >> + if (overlay->path[0] != '\0' || overlay->dtbo_size > 0) >> + return -EPERM; >> + >> + /* copy to path buffer (and make sure it's always zero terminated */ >> + count = snprintf(overlay->path, sizeof(overlay->path) - 1, "%s", p); >> + overlay->path[sizeof(overlay->path) - 1] = '\0'; >> + >> + /* strip trailing newlines */ >> + s = overlay->path + strlen(overlay->path); >> + while (s > overlay->path && *--s == '\n') >> + *s = '\0'; >> + >> + pr_debug("%s: path is '%s'\n", __func__, overlay->path); >> + >> + err = request_firmware(&overlay->fw, overlay->path, NULL); >> + if (err != 0) >> + goto out_err; >> + >> + err = create_overlay(overlay, (void *)overlay->fw->data); >> + if (err != 0) >> + goto out_err; >> + >> + return count; >> + >> +out_err: >> + >> + release_firmware(overlay->fw); >> + overlay->fw = NULL; >> + >> + overlay->path[0] = '\0'; >> + return err; >> +} >> + >> +static ssize_t cfs_overlay_item_status_show(struct cfs_overlay_item *overlay, >> + char *page) >> +{ >> + return sprintf(page, "%s\n", >> + overlay->ov_id >= 0 ? "applied" : "unapplied"); >> +} >> + >> +CFS_OVERLAY_ITEM_ATTR(path, S_IRUGO | S_IWUSR, >> + cfs_overlay_item_path_show, cfs_overlay_item_path_store); > > World writable? Am I reading this correctly? > Err, user writeable, world readable. “-rw-r--r—" > DT modifications are privileged. A user can potentially get arbitrary > access to i2c, spi, gpio or other things that shouldn't be allowed. This > feature give access right into the Linux driver model. > Yes, it does. > Before this can be merged, it needs to be locked down, and there needs > to be documentation about how it is locked down. Owned by root is only > the first step, there also needs to be some rules about which nodes can > be modified by the configfs interface. By default think no modifications > should be allowed on a tree unless there are properties somewhere in the > tree that explicitly allow modifications to be performed. > TBH this is more of a debug level interface. The way I see it a different overlay manager, that’s tuned to the platform, should handle the overlay request and application, in a manner that’s not directly open to user control. For example in a beaglebone you’d have a ‘cape’ manager reading the i2c eeproms and request the overlays they match without any user-space implication. However, this is an interface that developers will use daily, so I agree that we need to look into the security model now before it’s too late. How do you feel for something like this in chosen: overlay-targets = “/ocp”, “/pinctrl”; That would allow overlays to target the ocp and pinctrl nodes (and all their children). To allow overlays to attach everywhere just use overlay-targets = “/“; > Regardless, there needs to be a proposal made about the security model > so that it can be discussed and analyzed by folks better versed in > security that either of us. I would like to get Kees Cook to take a look > at what we are doing here. > Admittedly we could use some help here. >> +CFS_OVERLAY_ITEM_ATTR_RO(status, cfs_overlay_item_status_show); >> + >> +static struct configfs_attribute *cfs_overlay_attrs[] = { >> + &cfs_overlay_item_attr_path.attr, >> + &cfs_overlay_item_attr_status.attr, >> + NULL, >> +}; >> + >> +ssize_t cfs_overlay_item_dtbo_read(struct cfs_overlay_item *overlay, >> + void *buf, size_t max_count) >> +{ >> + pr_debug("%s: buf=%p max_count=%u\n", __func__, >> + buf, max_count); >> + >> + if (overlay->dtbo == NULL) >> + return 0; >> + >> + /* copy if buffer provided */ >> + if (buf != NULL) { >> + /* the buffer must be large enough */ >> + if (overlay->dtbo_size > max_count) >> + return -ENOSPC; >> + >> + memcpy(buf, overlay->dtbo, overlay->dtbo_size); >> + } >> + >> + return overlay->dtbo_size; >> +} >> + >> +ssize_t cfs_overlay_item_dtbo_write(struct cfs_overlay_item *overlay, >> + const void *buf, size_t count) >> +{ >> + int err; >> + >> + /* if it's set do not allow changes */ >> + if (overlay->path[0] != '\0' || overlay->dtbo_size > 0) >> + return -EPERM; >> + >> + /* copy the contents */ >> + overlay->dtbo = kmemdup(buf, count, GFP_KERNEL); >> + if (overlay->dtbo == NULL) >> + return -ENOMEM; >> + >> + overlay->dtbo_size = count; >> + >> + err = create_overlay(overlay, overlay->dtbo); >> + if (err != 0) >> + goto out_err; >> + >> + return count; >> + >> +out_err: >> + kfree(overlay->dtbo); >> + overlay->dtbo = NULL; >> + overlay->dtbo_size = 0; >> + >> + return err; >> +} >> + >> +CFS_OVERLAY_ITEM_BIN_ATTR(dtbo, S_IRUGO | S_IWUSR, >> + cfs_overlay_item_dtbo_read, cfs_overlay_item_dtbo_write, >> + NULL, SZ_1M); >> + >> +static struct configfs_bin_attribute *cfs_overlay_bin_attrs[] = { >> + &cfs_overlay_item_bin_attr_dtbo.bin_attr, >> + NULL, >> +}; >> + >> +static void cfs_overlay_release(struct config_item *item) >> +{ >> + struct cfs_overlay_item *overlay = to_cfs_overlay_item(item); >> + >> + if (overlay->ov_id >= 0) >> + of_overlay_destroy(overlay->ov_id); >> + if (overlay->fw) >> + release_firmware(overlay->fw); >> + /* kfree with NULL is safe */ >> + kfree(overlay->dtbo); >> + kfree(overlay); >> +} >> + >> +CONFIGFS_ATTR_OPS(cfs_overlay_item); >> +CONFIGFS_BIN_ATTR_OPS(cfs_overlay_item); >> +static struct configfs_item_operations cfs_overlay_item_ops = { >> + .release = cfs_overlay_release, >> + .show_attribute = cfs_overlay_item_attr_show, >> + .store_attribute = cfs_overlay_item_attr_store, >> + .read_bin_attribute = cfs_overlay_item_bin_attr_read, >> + .write_bin_attribute = cfs_overlay_item_bin_attr_write, >> +}; >> + >> +static struct config_item_type cfs_overlay_type = { >> + .ct_item_ops = &cfs_overlay_item_ops, >> + .ct_attrs = cfs_overlay_attrs, >> + .ct_bin_attrs = cfs_overlay_bin_attrs, >> + .ct_owner = THIS_MODULE, >> +}; >> + >> +static struct config_item *cfs_overlay_group_make_item( >> + struct config_group *group, const char *name) >> +{ >> + struct cfs_overlay_item *overlay; >> + >> + overlay = kzalloc(sizeof(*overlay), GFP_KERNEL); >> + if (!overlay) >> + return ERR_PTR(-ENOMEM); >> + overlay->ov_id = -1; >> + >> + config_item_init_type_name(&overlay->item, name, &cfs_overlay_type); >> + return &overlay->item; >> +} >> + >> +static void cfs_overlay_group_drop_item(struct config_group *group, >> + struct config_item *item) >> +{ >> + struct cfs_overlay_item *overlay = to_cfs_overlay_item(item); >> + >> + config_item_put(&overlay->item); >> +} >> + >> +static struct configfs_group_operations overlays_ops = { >> + .make_item = cfs_overlay_group_make_item, >> + .drop_item = cfs_overlay_group_drop_item, >> +}; >> + >> +static struct config_item_type overlays_type = { >> + .ct_group_ops = &overlays_ops, >> + .ct_owner = THIS_MODULE, >> +}; >> + >> +#endif /* CONFIG_OF_OVERLAY */ >> + >> +static struct configfs_group_operations of_cfs_ops = { >> + /* empty - we don't allow anything to be created */ >> +}; >> + >> +static struct config_item_type of_cfs_type = { >> + .ct_group_ops = &of_cfs_ops, >> + .ct_owner = THIS_MODULE, >> +}; >> + >> +struct config_group of_cfs_overlay_group; >> + >> +struct config_group *of_cfs_def_groups[] = { >> +#ifdef CONFIG_OF_OVERLAY >> + &of_cfs_overlay_group, >> +#endif >> + NULL >> +}; >> + >> +static struct configfs_subsystem of_cfs_subsys = { >> + .su_group = { >> + .cg_item = { >> + .ci_namebuf = "device-tree", >> + .ci_type = &of_cfs_type, >> + }, >> + .default_groups = of_cfs_def_groups, >> + }, >> + .su_mutex = __MUTEX_INITIALIZER(of_cfs_subsys.su_mutex), >> +}; >> + >> +static int __init of_cfs_init(void) >> +{ >> + int ret; >> + >> + pr_info("%s\n", __func__); >> + >> + config_group_init(&of_cfs_subsys.su_group); >> +#ifdef CONFIG_OF_OVERLAY >> + config_group_init_type_name(&of_cfs_overlay_group, "overlays", >> + &overlays_type); >> +#endif >> + >> + ret = configfs_register_subsystem(&of_cfs_subsys); >> + if (ret != 0) { >> + pr_err("%s: failed to register subsys\n", __func__); >> + goto out; >> + } >> + pr_info("%s: OK\n", __func__); >> +out: >> + return ret; >> +} >> +late_initcall(of_cfs_init); >> -- >> 1.7.12 >> Regards — Pantelis -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/