android_kernel_motorola_sm6225/security/device_cgroup.c
Serge E. Hallyn 0b82ac37b8 devices cgroup: allow mkfifo
The devcgroup_inode_permission() hook in the devices whitelist cgroup has
always bypassed access checks on fifos.  But the mknod hook did not.  The
devices whitelist is only about block and char devices, and fifos can't
even be added to the whitelist, so fifos can't be created at all except by
tasks which have 'a' in their whitelist (meaning they have access to all
devices).

Fix the behavior by bypassing access checks to mkfifo.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Paul Menage <menage@google.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: James Morris <jmorris@namei.org>
Reported-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Cc: <stable@kernel.org>		[2.6.27.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-08 08:31:03 -08:00

544 lines
12 KiB
C

/*
* device_cgroup.c - device cgroup subsystem
*
* Copyright 2007 IBM Corp
*/
#include <linux/device_cgroup.h>
#include <linux/cgroup.h>
#include <linux/ctype.h>
#include <linux/list.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
#include <linux/rcupdate.h>
#define ACC_MKNOD 1
#define ACC_READ 2
#define ACC_WRITE 4
#define ACC_MASK (ACC_MKNOD | ACC_READ | ACC_WRITE)
#define DEV_BLOCK 1
#define DEV_CHAR 2
#define DEV_ALL 4 /* this represents all devices */
/*
* whitelist locking rules:
* hold cgroup_lock() for update/read.
* hold rcu_read_lock() for read.
*/
struct dev_whitelist_item {
u32 major, minor;
short type;
short access;
struct list_head list;
struct rcu_head rcu;
};
struct dev_cgroup {
struct cgroup_subsys_state css;
struct list_head whitelist;
};
static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
{
return container_of(s, struct dev_cgroup, css);
}
static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
{
return css_to_devcgroup(cgroup_subsys_state(cgroup, devices_subsys_id));
}
static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
{
return css_to_devcgroup(task_subsys_state(task, devices_subsys_id));
}
struct cgroup_subsys devices_subsys;
static int devcgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup, struct task_struct *task)
{
if (current != task && !capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}
/*
* called under cgroup_lock()
*/
static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig)
{
struct dev_whitelist_item *wh, *tmp, *new;
list_for_each_entry(wh, orig, list) {
new = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
if (!new)
goto free_and_exit;
list_add_tail(&new->list, dest);
}
return 0;
free_and_exit:
list_for_each_entry_safe(wh, tmp, dest, list) {
list_del(&wh->list);
kfree(wh);
}
return -ENOMEM;
}
/* Stupid prototype - don't bother combining existing entries */
/*
* called under cgroup_lock()
*/
static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
struct dev_whitelist_item *wh)
{
struct dev_whitelist_item *whcopy, *walk;
whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
if (!whcopy)
return -ENOMEM;
list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
if (walk->type != wh->type)
continue;
if (walk->major != wh->major)
continue;
if (walk->minor != wh->minor)
continue;
walk->access |= wh->access;
kfree(whcopy);
whcopy = NULL;
}
if (whcopy != NULL)
list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
return 0;
}
static void whitelist_item_free(struct rcu_head *rcu)
{
struct dev_whitelist_item *item;
item = container_of(rcu, struct dev_whitelist_item, rcu);
kfree(item);
}
/*
* called under cgroup_lock()
*/
static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
struct dev_whitelist_item *wh)
{
struct dev_whitelist_item *walk, *tmp;
list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
if (walk->type == DEV_ALL)
goto remove;
if (walk->type != wh->type)
continue;
if (walk->major != ~0 && walk->major != wh->major)
continue;
if (walk->minor != ~0 && walk->minor != wh->minor)
continue;
remove:
walk->access &= ~wh->access;
if (!walk->access) {
list_del_rcu(&walk->list);
call_rcu(&walk->rcu, whitelist_item_free);
}
}
}
/*
* called from kernel/cgroup.c with cgroup_lock() held.
*/
static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct dev_cgroup *dev_cgroup, *parent_dev_cgroup;
struct cgroup *parent_cgroup;
int ret;
dev_cgroup = kzalloc(sizeof(*dev_cgroup), GFP_KERNEL);
if (!dev_cgroup)
return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&dev_cgroup->whitelist);
parent_cgroup = cgroup->parent;
if (parent_cgroup == NULL) {
struct dev_whitelist_item *wh;
wh = kmalloc(sizeof(*wh), GFP_KERNEL);
if (!wh) {
kfree(dev_cgroup);
return ERR_PTR(-ENOMEM);
}
wh->minor = wh->major = ~0;
wh->type = DEV_ALL;
wh->access = ACC_MASK;
list_add(&wh->list, &dev_cgroup->whitelist);
} else {
parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
ret = dev_whitelist_copy(&dev_cgroup->whitelist,
&parent_dev_cgroup->whitelist);
if (ret) {
kfree(dev_cgroup);
return ERR_PTR(ret);
}
}
return &dev_cgroup->css;
}
static void devcgroup_destroy(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct dev_cgroup *dev_cgroup;
struct dev_whitelist_item *wh, *tmp;
dev_cgroup = cgroup_to_devcgroup(cgroup);
list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
list_del(&wh->list);
kfree(wh);
}
kfree(dev_cgroup);
}
#define DEVCG_ALLOW 1
#define DEVCG_DENY 2
#define DEVCG_LIST 3
#define MAJMINLEN 13
#define ACCLEN 4
static void set_access(char *acc, short access)
{
int idx = 0;
memset(acc, 0, ACCLEN);
if (access & ACC_READ)
acc[idx++] = 'r';
if (access & ACC_WRITE)
acc[idx++] = 'w';
if (access & ACC_MKNOD)
acc[idx++] = 'm';
}
static char type_to_char(short type)
{
if (type == DEV_ALL)
return 'a';
if (type == DEV_CHAR)
return 'c';
if (type == DEV_BLOCK)
return 'b';
return 'X';
}
static void set_majmin(char *str, unsigned m)
{
if (m == ~0)
strcpy(str, "*");
else
sprintf(str, "%u", m);
}
static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
struct seq_file *m)
{
struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
struct dev_whitelist_item *wh;
char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
rcu_read_lock();
list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) {
set_access(acc, wh->access);
set_majmin(maj, wh->major);
set_majmin(min, wh->minor);
seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type),
maj, min, acc);
}
rcu_read_unlock();
return 0;
}
/*
* may_access_whitelist:
* does the access granted to dev_cgroup c contain the access
* requested in whitelist item refwh.
* return 1 if yes, 0 if no.
* call with c->lock held
*/
static int may_access_whitelist(struct dev_cgroup *c,
struct dev_whitelist_item *refwh)
{
struct dev_whitelist_item *whitem;
list_for_each_entry(whitem, &c->whitelist, list) {
if (whitem->type & DEV_ALL)
return 1;
if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))
continue;
if ((refwh->type & DEV_CHAR) && !(whitem->type & DEV_CHAR))
continue;
if (whitem->major != ~0 && whitem->major != refwh->major)
continue;
if (whitem->minor != ~0 && whitem->minor != refwh->minor)
continue;
if (refwh->access & (~whitem->access))
continue;
return 1;
}
return 0;
}
/*
* parent_has_perm:
* when adding a new allow rule to a device whitelist, the rule
* must be allowed in the parent device
*/
static int parent_has_perm(struct dev_cgroup *childcg,
struct dev_whitelist_item *wh)
{
struct cgroup *pcg = childcg->css.cgroup->parent;
struct dev_cgroup *parent;
if (!pcg)
return 1;
parent = cgroup_to_devcgroup(pcg);
return may_access_whitelist(parent, wh);
}
/*
* Modify the whitelist using allow/deny rules.
* CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
* so we can give a container CAP_MKNOD to let it create devices but not
* modify the whitelist.
* It seems likely we'll want to add a CAP_CONTAINER capability to allow
* us to also grant CAP_SYS_ADMIN to containers without giving away the
* device whitelist controls, but for now we'll stick with CAP_SYS_ADMIN
*
* Taking rules away is always allowed (given CAP_SYS_ADMIN). Granting
* new access is only allowed if you're in the top-level cgroup, or your
* parent cgroup has the access you're asking for.
*/
static int devcgroup_update_access(struct dev_cgroup *devcgroup,
int filetype, const char *buffer)
{
const char *b;
char *endp;
int count;
struct dev_whitelist_item wh;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
memset(&wh, 0, sizeof(wh));
b = buffer;
switch (*b) {
case 'a':
wh.type = DEV_ALL;
wh.access = ACC_MASK;
wh.major = ~0;
wh.minor = ~0;
goto handle;
case 'b':
wh.type = DEV_BLOCK;
break;
case 'c':
wh.type = DEV_CHAR;
break;
default:
return -EINVAL;
}
b++;
if (!isspace(*b))
return -EINVAL;
b++;
if (*b == '*') {
wh.major = ~0;
b++;
} else if (isdigit(*b)) {
wh.major = simple_strtoul(b, &endp, 10);
b = endp;
} else {
return -EINVAL;
}
if (*b != ':')
return -EINVAL;
b++;
/* read minor */
if (*b == '*') {
wh.minor = ~0;
b++;
} else if (isdigit(*b)) {
wh.minor = simple_strtoul(b, &endp, 10);
b = endp;
} else {
return -EINVAL;
}
if (!isspace(*b))
return -EINVAL;
for (b++, count = 0; count < 3; count++, b++) {
switch (*b) {
case 'r':
wh.access |= ACC_READ;
break;
case 'w':
wh.access |= ACC_WRITE;
break;
case 'm':
wh.access |= ACC_MKNOD;
break;
case '\n':
case '\0':
count = 3;
break;
default:
return -EINVAL;
}
}
handle:
switch (filetype) {
case DEVCG_ALLOW:
if (!parent_has_perm(devcgroup, &wh))
return -EPERM;
return dev_whitelist_add(devcgroup, &wh);
case DEVCG_DENY:
dev_whitelist_rm(devcgroup, &wh);
break;
default:
return -EINVAL;
}
return 0;
}
static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
const char *buffer)
{
int retval;
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
cft->private, buffer);
cgroup_unlock();
return retval;
}
static struct cftype dev_cgroup_files[] = {
{
.name = "allow",
.write_string = devcgroup_access_write,
.private = DEVCG_ALLOW,
},
{
.name = "deny",
.write_string = devcgroup_access_write,
.private = DEVCG_DENY,
},
{
.name = "list",
.read_seq_string = devcgroup_seq_read,
.private = DEVCG_LIST,
},
};
static int devcgroup_populate(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
return cgroup_add_files(cgroup, ss, dev_cgroup_files,
ARRAY_SIZE(dev_cgroup_files));
}
struct cgroup_subsys devices_subsys = {
.name = "devices",
.can_attach = devcgroup_can_attach,
.create = devcgroup_create,
.destroy = devcgroup_destroy,
.populate = devcgroup_populate,
.subsys_id = devices_subsys_id,
};
int devcgroup_inode_permission(struct inode *inode, int mask)
{
struct dev_cgroup *dev_cgroup;
struct dev_whitelist_item *wh;
dev_t device = inode->i_rdev;
if (!device)
return 0;
if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
return 0;
rcu_read_lock();
dev_cgroup = task_devcgroup(current);
list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
if (wh->type & DEV_ALL)
goto acc_check;
if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
continue;
if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
continue;
if (wh->major != ~0 && wh->major != imajor(inode))
continue;
if (wh->minor != ~0 && wh->minor != iminor(inode))
continue;
acc_check:
if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
continue;
if ((mask & MAY_READ) && !(wh->access & ACC_READ))
continue;
rcu_read_unlock();
return 0;
}
rcu_read_unlock();
return -EPERM;
}
int devcgroup_inode_mknod(int mode, dev_t dev)
{
struct dev_cgroup *dev_cgroup;
struct dev_whitelist_item *wh;
if (!S_ISBLK(mode) && !S_ISCHR(mode))
return 0;
rcu_read_lock();
dev_cgroup = task_devcgroup(current);
list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
if (wh->type & DEV_ALL)
goto acc_check;
if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
continue;
if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
continue;
if (wh->major != ~0 && wh->major != MAJOR(dev))
continue;
if (wh->minor != ~0 && wh->minor != MINOR(dev))
continue;
acc_check:
if (!(wh->access & ACC_MKNOD))
continue;
rcu_read_unlock();
return 0;
}
rcu_read_unlock();
return -EPERM;
}