[RFC][PATCH] Devices visibility container
Pavel Emelyanov
xemul at openvz.org
Mon Sep 24 01:28:19 PDT 2007
Hi.
At KS we have pointed out the need in some container, that allows
to limit the visibility of some devices to task within it. I.e.
allow for /dev/null, /dev/zero etc, but disable (by default) some
IDE devices or SCSI discs and so on.
Here's the beta of the container. Currently this only allows to
hide the _character_ devices only from the living tasks. To play
with it you just create the container like this
# mount -t container none /cont/devs -o devices
# mkdir /cont/devs/0
it will have two specific files
# ls /cont/devs
devices.block devices.char notify_on_release releasable release_agent tasks
then move a task into it
# /bin/echo -n $$ > /cont/devs/0/tasks
after this you won't be able to read from even /dev/zero
# hexdump /dev/zero
hexdump: /dev/zero: No such device or address
hexdump: /dev/zero: Bad file descriptor
meanwhile from another ssh session you will. You may allow access
to /dev/zero like this
# /bin/echo -n '+1:5' > /cont/devs/0/devices.char
More generally, the '+<major>:<minor>' string grants access to
some device, and '-<major>:<minor>' disables one.
The TODO list now looks like this:
* add the block devices support :) don't know how to make it yet;
* make /proc/devices show relevant info depending on who is
reading it. currently even if major 1 is disabled for task,
it will be listed in this file;
* make it possible to enable/disable not just individual major:minor
pair, but something more flexible, e.g. major:* for all minors
for given major or major:m1-m2 for minor range, etc;
* add the ability to restrict the read/write permissions for a
container. currently one may just control the visible-invisible
state for a device in a container, but maybe just readable or
just writable would be better.
This patch is minimally tested, because I just want to know your
opinion on whether it worths developing the container in such a way or not.
Signed-off-by: Pavel Emelyanov <xemul at openvz.org>
---
diff --git a/drivers/base/map.c b/drivers/base/map.c
index e87017f..0188053 100644
--- a/drivers/base/map.c
+++ b/drivers/base/map.c
@@ -153,3 +153,21 @@ struct kobj_map *kobj_map_init(kobj_prob
p->lock = lock;
return p;
}
+
+void kobj_map_fini(struct kobj_map *map)
+{
+ int i;
+ struct probe *p, *next;
+
+ for (i = 0; i < 256; i++) {
+ p = map->probes[i];
+ while (p->next != NULL) {
+ next = p->next;
+ kfree(p);
+ p = next;
+ }
+ }
+
+ kfree(p);
+ kfree(map);
+}
diff --git a/fs/Makefile b/fs/Makefile
index 2661ef9..837c731 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -64,6 +64,8 @@ obj-y += devpts/
obj-$(CONFIG_PROFILING) += dcookies.o
obj-$(CONFIG_DLM) += dlm/
+
+obj-$(CONFIG_CONTAINER_DEVS) += devscontrol.o
# Do not add any filesystems before this line
obj-$(CONFIG_REISERFS_FS) += reiserfs/
diff --git a/fs/char_dev.c b/fs/char_dev.c
index c3bfa76..1b0e4da 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -22,6 +22,8 @@
#include <linux/mutex.h>
#include <linux/backing-dev.h>
+#include <linux/devscontrol.h>
+
#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif
@@ -362,17 +364,24 @@ int chrdev_open(struct inode * inode, st
struct cdev *p;
struct cdev *new = NULL;
int ret = 0;
+ struct kobj_map *map;
+
+ map = task_cdev_map(current);
+ if (map == NULL)
+ map = cdev_map;
spin_lock(&cdev_lock);
p = inode->i_cdev;
- if (!p) {
+ if (!p || p->last != map) {
struct kobject *kobj;
int idx;
+
spin_unlock(&cdev_lock);
- kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
+ kobj = kobj_lookup(map, inode->i_rdev, &idx);
if (!kobj)
return -ENXIO;
new = container_of(kobj, struct cdev, kobj);
+ BUG_ON(p != NULL && p != new);
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
@@ -384,6 +393,8 @@ int chrdev_open(struct inode * inode, st
ret = -ENXIO;
} else if (!cdev_get(p))
ret = -ENXIO;
+ if (p)
+ p->last = map;
spin_unlock(&cdev_lock);
cdev_put(new);
if (ret)
@@ -461,6 +472,49 @@ int cdev_add(struct cdev *p, dev_t dev,
return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
}
+int cdev_add_to_map(struct kobj_map *map, dev_t dev)
+{
+ int tmp;
+ struct kobject *k;
+ struct cdev *c;
+
+ k = kobj_lookup(cdev_map, dev, &tmp);
+ if (k == NULL)
+ return -ENODEV;
+
+ c = container_of(k, struct cdev, kobj);
+ tmp = kobj_map(map, dev, 1, NULL, exact_match, exact_lock, c);
+ if (tmp < 0) {
+ cdev_put(c);
+ return tmp;
+ }
+
+ return 0;
+}
+
+int cdev_del_from_map(struct kobj_map *map, dev_t dev)
+{
+ int tmp;
+ struct kobject *k;
+ struct cdev *c;
+
+ k = kobj_lookup(cdev_map, dev, &tmp);
+ if (k == NULL)
+ return -ENODEV;
+
+ c = container_of(k, struct cdev, kobj);
+ kobj_unmap(map, dev, 1);
+
+ spin_lock(&cdev_lock);
+ if (c->last == map)
+ c->last = NULL;
+ spin_unlock(&cdev_lock);
+
+ cdev_put(c);
+ cdev_put(c);
+ return 0;
+}
+
static void cdev_unmap(dev_t dev, unsigned count)
{
kobj_unmap(cdev_map, dev, count);
@@ -542,6 +596,16 @@ static struct kobject *base_probe(dev_t
return NULL;
}
+struct kobj_map *cdev_map_init(void)
+{
+ return kobj_map_init(base_probe, &chrdevs_lock);
+}
+
+void cdev_map_fini(struct kobj_map *map)
+{
+ kobj_map_fini(map);
+}
+
void __init chrdev_init(void)
{
cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
diff --git a/fs/devscontrol.c b/fs/devscontrol.c
new file mode 100644
index 0000000..6fb5f05
--- /dev/null
+++ b/fs/devscontrol.c
@@ -0,0 +1,170 @@
+/*
+ * devscontrol.c - Device Controller
+ *
+ * Copyright 2007 OpenVZ SWsoft Inc
+ * Author: Pavel Emelyanov <xemul at openvz.org>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/container.h>
+#include <linux/cdev.h>
+#include <linux/err.h>
+#include <linux/devscontrol.h>
+#include <linux/uaccess.h>
+
+struct devs_container {
+ struct container_subsys_state css;
+
+ struct kobj_map *cdev_map;
+};
+
+static inline
+struct devs_container *css_to_devs(struct container_subsys_state *css)
+{
+ return container_of(css, struct devs_container, css);
+}
+
+static inline
+struct devs_container *container_to_devs(struct container *cont)
+{
+ return css_to_devs(container_subsys_state(cont, devs_subsys_id));
+}
+
+struct kobj_map *task_cdev_map(struct task_struct *tsk)
+{
+ struct container_subsys_state *css;
+
+ css = task_subsys_state(tsk, devs_subsys_id);
+ if (css->container->parent == NULL)
+ return NULL;
+ else
+ return css_to_devs(css)->cdev_map;
+}
+
+static struct container_subsys_state *
+devs_create(struct container_subsys *ss, struct container *cont)
+{
+ struct devs_container *devs;
+
+ devs = kzalloc(sizeof(struct devs_container), GFP_KERNEL);
+ if (devs == NULL)
+ goto out;
+
+ devs->cdev_map = cdev_map_init();
+ if (devs->cdev_map == NULL)
+ goto out_free;
+
+ return &devs->css;
+
+out_free:
+ kfree(devs);
+out:
+ return ERR_PTR(-ENOMEM);
+}
+
+static void devs_destroy(struct container_subsys *ss, struct container *cont)
+{
+ struct devs_container *devs;
+
+ devs = container_to_devs(cont);
+ cdev_map_fini(devs->cdev_map);
+ kfree(devs);
+}
+
+static int decode_dev_name(char *buf, dev_t *dev)
+{
+ unsigned int major, minor;
+ char *end;
+
+ major = simple_strtoul(buf, &end, 10);
+ if (*end != ':')
+ return -EINVAL;
+
+ minor = simple_strtoul(end + 1, &end, 10);
+ if (*end != '\0')
+ return -EINVAL;
+
+ *dev = MKDEV(major, minor);
+ return 0;
+}
+
+static ssize_t
+devs_char_write(struct container *cont, struct cftype *cft, struct file *f,
+ const char __user *userbuf, size_t nbytes, loff_t *pos)
+{
+ int err;
+ dev_t dev;
+ char buf[64];
+ struct devs_container *devs;
+
+ if (copy_from_user(buf, userbuf, sizeof(buf)))
+ return -EFAULT;
+
+ err = decode_dev_name(buf + 1, &dev);
+ if (err < 0)
+ return err;
+
+ devs = container_to_devs(cont);
+
+ switch (buf[0]) {
+ case '+':
+ err = cdev_add_to_map(devs->cdev_map, dev);
+ if (err < 0)
+ return err;
+
+ css_get(&devs->css);
+ break;
+ case '-':
+ err = cdev_del_from_map(devs->cdev_map, dev);
+ if (err < 0)
+ return err;
+
+ css_put(&devs->css);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return nbytes;
+}
+
+static ssize_t
+devs_block_write(struct container *cont, struct cftype *cft, struct file *f,
+ const char __user *userbuf, size_t nbytes, loff_t *pos)
+{
+ return -ENOTTY;
+}
+
+static struct cftype devs_files[] = {
+ {
+ .name = "char",
+ .write = devs_char_write,
+ },
+ {
+ .name = "block",
+ .write = devs_block_write,
+ },
+};
+
+static int devs_populate(struct container_subsys *ss, struct container *cont)
+{
+ return container_add_files(cont, ss,
+ devs_files, ARRAY_SIZE(devs_files));
+}
+
+struct container_subsys devs_subsys = {
+ .name = "devices",
+ .subsys_id = devs_subsys_id,
+ .create = devs_create,
+ .destroy = devs_destroy,
+ .populate = devs_populate,
+};
diff --git a/include/linux/cdev.h b/include/linux/cdev.h
index 1e29b13..0eded40 100644
--- a/include/linux/cdev.h
+++ b/include/linux/cdev.h
@@ -9,6 +9,7 @@
struct file_operations;
struct inode;
struct module;
+struct kobj_map;
struct cdev {
struct kobject kobj;
@@ -17,6 +18,7 @@ struct cdev {
struct list_head list;
dev_t dev;
unsigned int count;
+ struct kobj_map *last;
};
void cdev_init(struct cdev *, const struct file_operations *);
@@ -33,5 +35,9 @@ void cd_forget(struct inode *);
extern struct backing_dev_info directly_mappable_cdev_bdi;
+int cdev_add_to_map(struct kobj_map *map, dev_t dev);
+int cdev_del_from_map(struct kobj_map *map, dev_t dev);
+struct kobj_map *cdev_map_init(void);
+void cdev_map_fini(struct kobj_map *map);
#endif
#endif
diff --git a/include/linux/container_subsys.h b/include/linux/container_subsys.h
index 81d11c2..9315a9b 100644
--- a/include/linux/container_subsys.h
+++ b/include/linux/container_subsys.h
@@ -36,3 +36,9 @@ SUBSYS(mem_container)
#endif
/* */
+
+#ifdef CONFIG_CONTAINER_DEVS
+SUBSYS(devs)
+#endif
+
+/* */
diff --git a/include/linux/devscontrol.h b/include/linux/devscontrol.h
new file mode 100644
index 0000000..51ae916
--- /dev/null
+++ b/include/linux/devscontrol.h
@@ -0,0 +1,14 @@
+#ifndef __DEVS_CONTROL_H__
+#define __DEVS_CONTROL_H__
+struct kobj_map;
+struct task_struct;
+
+#ifdef CONFIG_CONTAINER_DEVS
+struct kobj_map *task_cdev_map(struct task_struct *);
+#else
+static inline kobj_map *task_cdev_map(struct task_struct *tsk)
+{
+ return NULL;
+}
+#endif
+#endif
diff --git a/include/linux/kobj_map.h b/include/linux/kobj_map.h
index bafe178..2476f8d 100644
--- a/include/linux/kobj_map.h
+++ b/include/linux/kobj_map.h
@@ -10,5 +10,6 @@ int kobj_map(struct kobj_map *, dev_t, u
void kobj_unmap(struct kobj_map *, dev_t, unsigned long);
struct kobject *kobj_lookup(struct kobj_map *, dev_t, int *);
struct kobj_map *kobj_map_init(kobj_probe_t *, struct mutex *);
+void kobj_map_fini(struct kobj_map *);
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 0bb211a..5e1158e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -292,6 +292,12 @@ config CONTAINER_DEBUG
Say N if unsure
+config CONTAINER_DEVS
+ bool "Devices container subsystem"
+ depends on CONTAINERS
+ help
+ Controlls the visibility of devices
+
config CONTAINER_NS
bool "Namespace container subsystem"
depends on CONTAINERS
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