--- /dev/null
+/*
+ * dev_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>
+
+#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:
+ * cgroup_lock() cannot be taken under dev_cgroup->lock.
+ * dev_cgroup->lock can be taken with or without cgroup_lock().
+ *
+ * modifications always require cgroup_lock
+ * modifications to a list which is visible require the
+ * dev_cgroup->lock *and* cgroup_lock()
+ * walking the list requires dev_cgroup->lock or cgroup_lock().
+ *
+ * reasoning: dev_whitelist_copy() needs to kmalloc, so needs
+ * a mutex, which the cgroup_lock() is. Since modifying
+ * a visible list requires both locks, either lock can be
+ * taken for walking the list.
+ */
+
+struct dev_whitelist_item {
+ u32 major, minor;
+ short type;
+ short access;
+ struct list_head list;
+};
+
+struct dev_cgroup {
+ struct cgroup_subsys_state css;
+ struct list_head whitelist;
+ spinlock_t lock;
+};
+
+static inline struct dev_cgroup *cgroup_to_devcgroup(struct cgroup *cgroup)
+{
+ return container_of(cgroup_subsys_state(cgroup, devices_subsys_id),
+ struct dev_cgroup, css);
+}
+
+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 = kmalloc(sizeof(*wh), GFP_KERNEL);
+ if (!new)
+ goto free_and_exit;
+ new->major = wh->major;
+ new->minor = wh->minor;
+ new->type = wh->type;
+ new->access = wh->access;
+ 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()
+ * since the list is visible to other tasks, we need the spinlock also
+ */
+static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
+ struct dev_whitelist_item *wh)
+{
+ struct dev_whitelist_item *whcopy;
+
+ whcopy = kmalloc(sizeof(*whcopy), GFP_KERNEL);
+ if (!whcopy)
+ return -ENOMEM;
+
+ memcpy(whcopy, wh, sizeof(*whcopy));
+ spin_lock(&dev_cgroup->lock);
+ list_add_tail(&whcopy->list, &dev_cgroup->whitelist);
+ spin_unlock(&dev_cgroup->lock);
+ return 0;
+}
+
+/*
+ * called under cgroup_lock()
+ * since the list is visible to other tasks, we need the spinlock also
+ */
+static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
+ struct dev_whitelist_item *wh)
+{
+ struct dev_whitelist_item *walk, *tmp;
+
+ spin_lock(&dev_cgroup->lock);
+ 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(&walk->list);
+ kfree(walk);
+ }
+ }
+ spin_unlock(&dev_cgroup->lock);
+}
+
+/*
+ * 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_MKNOD | ACC_READ | ACC_WRITE;
+ 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);
+ }
+ }
+
+ spin_lock_init(&dev_cgroup->lock);
+ 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
+
+static void set_access(char *acc, short access)
+{
+ int idx = 0;
+ memset(acc, 0, 4);
+ 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, int len, unsigned m)
+{
+ memset(str, 0, len);
+ if (m == ~0)
+ sprintf(str, "*");
+ else
+ snprintf(str, len, "%d", m);
+}
+
+static char *print_whitelist(struct dev_cgroup *devcgroup, int *len)
+{
+ char *buf, *s, acc[4];
+ struct dev_whitelist_item *wh;
+ int ret;
+ int count = 0;
+ char maj[10], min[10];
+
+ buf = kmalloc(4096, GFP_KERNEL);
+ if (!buf)
+ return ERR_PTR(-ENOMEM);
+ s = buf;
+ *s = '\0';
+ *len = 0;
+
+ spin_lock(&devcgroup->lock);
+ list_for_each_entry(wh, &devcgroup->whitelist, list) {
+ set_access(acc, wh->access);
+ set_majmin(maj, 10, wh->major);
+ set_majmin(min, 10, wh->minor);
+ ret = snprintf(s, 4095-(s-buf), "%c %s:%s %s\n",
+ type_to_char(wh->type), maj, min, acc);
+ if (s+ret >= buf+4095) {
+ kfree(buf);
+ buf = ERR_PTR(-ENOMEM);
+ break;
+ }
+ s += ret;
+ *len += ret;
+ count++;
+ }
+ spin_unlock(&devcgroup->lock);
+
+ return buf;
+}
+
+static ssize_t devcgroup_access_read(struct cgroup *cgroup,
+ struct cftype *cft, struct file *file,
+ char __user *userbuf, size_t nbytes, loff_t *ppos)
+{
+ struct dev_cgroup *devcgroup = cgroup_to_devcgroup(cgroup);
+ int filetype = cft->private;
+ char *buffer;
+ int uninitialized_var(len);
+ int retval;
+
+ if (filetype != DEVCG_ALLOW)
+ return -EINVAL;
+ buffer = print_whitelist(devcgroup, &len);
+ if (IS_ERR(buffer))
+ return PTR_ERR(buffer);
+
+ retval = simple_read_from_buffer(userbuf, nbytes, ppos, buffer, len);
+ kfree(buffer);
+ return retval;
+}
+
+/*
+ * 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 | ACC_MASK)))
+ 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 cgroup *childcg,
+ struct dev_whitelist_item *wh)
+{
+ struct cgroup *pcg = childcg->parent;
+ struct dev_cgroup *parent;
+ int ret;
+
+ if (!pcg)
+ return 1;
+ parent = cgroup_to_devcgroup(pcg);
+ spin_lock(&parent->lock);
+ ret = may_access_whitelist(parent, wh);
+ spin_unlock(&parent->lock);
+ return ret;
+}
+
+/*
+ * 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 ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
+ struct file *file, const char __user *userbuf,
+ size_t nbytes, loff_t *ppos)
+{
+ struct cgroup *cur_cgroup;
+ struct dev_cgroup *devcgroup, *cur_devcgroup;
+ int filetype = cft->private;
+ char *buffer, *b;
+ int retval = 0, count;
+ struct dev_whitelist_item wh;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ devcgroup = cgroup_to_devcgroup(cgroup);
+ cur_cgroup = task_cgroup(current, devices_subsys.subsys_id);
+ cur_devcgroup = cgroup_to_devcgroup(cur_cgroup);
+
+ buffer = kmalloc(nbytes+1, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+
+ if (copy_from_user(buffer, userbuf, nbytes)) {
+ retval = -EFAULT;
+ goto out1;
+ }
+ buffer[nbytes] = 0; /* nul-terminate */
+
+ cgroup_lock();
+ if (cgroup_is_removed(cgroup)) {
+ retval = -ENODEV;
+ goto out2;
+ }
+
+ memset(&wh, 0, sizeof(wh));
+ b = buffer;
+
+ switch (*b) {
+ case 'a':
+ wh.type = DEV_ALL;
+ wh.access = ACC_MASK;
+ goto handle;
+ case 'b':
+ wh.type = DEV_BLOCK;
+ break;
+ case 'c':
+ wh.type = DEV_CHAR;
+ break;
+ default:
+ retval = -EINVAL;
+ goto out2;
+ }
+ b++;
+ if (!isspace(*b)) {
+ retval = -EINVAL;
+ goto out2;
+ }
+ b++;
+ if (*b == '*') {
+ wh.major = ~0;
+ b++;
+ } else if (isdigit(*b)) {
+ wh.major = 0;
+ while (isdigit(*b)) {
+ wh.major = wh.major*10+(*b-'0');
+ b++;
+ }
+ } else {
+ retval = -EINVAL;
+ goto out2;
+ }
+ if (*b != ':') {
+ retval = -EINVAL;
+ goto out2;
+ }
+ b++;
+
+ /* read minor */
+ if (*b == '*') {
+ wh.minor = ~0;
+ b++;
+ } else if (isdigit(*b)) {
+ wh.minor = 0;
+ while (isdigit(*b)) {
+ wh.minor = wh.minor*10+(*b-'0');
+ b++;
+ }
+ } else {
+ retval = -EINVAL;
+ goto out2;
+ }
+ if (!isspace(*b)) {
+ retval = -EINVAL;
+ goto out2;
+ }
+ 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:
+ retval = -EINVAL;
+ goto out2;
+ }
+ }
+
+handle:
+ retval = 0;
+ switch (filetype) {
+ case DEVCG_ALLOW:
+ if (!parent_has_perm(cgroup, &wh))
+ retval = -EPERM;
+ else
+ retval = dev_whitelist_add(devcgroup, &wh);
+ break;
+ case DEVCG_DENY:
+ dev_whitelist_rm(devcgroup, &wh);
+ break;
+ default:
+ retval = -EINVAL;
+ goto out2;
+ }
+
+ if (retval == 0)
+ retval = nbytes;
+
+out2:
+ cgroup_unlock();
+out1:
+ kfree(buffer);
+ return retval;
+}
+
+static struct cftype dev_cgroup_files[] = {
+ {
+ .name = "allow",
+ .read = devcgroup_access_read,
+ .write = devcgroup_access_write,
+ .private = DEVCG_ALLOW,
+ },
+ {
+ .name = "deny",
+ .write = devcgroup_access_write,
+ .private = DEVCG_DENY,
+ },
+};
+
+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 cgroup *cgroup;
+ 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;
+ cgroup = task_cgroup(current, devices_subsys.subsys_id);
+ dev_cgroup = cgroup_to_devcgroup(cgroup);
+ if (!dev_cgroup)
+ return 0;
+
+ spin_lock(&dev_cgroup->lock);
+ list_for_each_entry(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;
+ spin_unlock(&dev_cgroup->lock);
+ return 0;
+ }
+ spin_unlock(&dev_cgroup->lock);
+
+ return -EPERM;
+}
+
+int devcgroup_inode_mknod(int mode, dev_t dev)
+{
+ struct cgroup *cgroup;
+ struct dev_cgroup *dev_cgroup;
+ struct dev_whitelist_item *wh;
+
+ cgroup = task_cgroup(current, devices_subsys.subsys_id);
+ dev_cgroup = cgroup_to_devcgroup(cgroup);
+ if (!dev_cgroup)
+ return 0;
+
+ spin_lock(&dev_cgroup->lock);
+ list_for_each_entry(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;
+ spin_unlock(&dev_cgroup->lock);
+ return 0;
+ }
+ spin_unlock(&dev_cgroup->lock);
+ return -EPERM;
+}
projects / users / hch / configfs.git / commitdiff