1 files changed, 575 insertions, 0 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
new file mode 100644
index 0000000..4ea5836
--- /dev/null
+++ b/security/device_cgroup.c
@@ -0,0 +1,575 @@
+/*
+ * 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>
+#include <linux/seq_file.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
+#define DEVCG_LIST 3
+
+#define MAJMINLEN 10
+#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)
+{
+	memset(str, 0, MAJMINLEN);
+	if (m == ~0)
+		sprintf(str, "*");
+	else
+		snprintf(str, MAJMINLEN, "%d", 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];
+
+	spin_lock(&devcgroup->lock);
+	list_for_each_entry(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);
+	}
+	spin_unlock(&devcgroup->lock);
+
+	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 | 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",
+		.write  = devcgroup_access_write,
+		.private = DEVCG_ALLOW,
+	},
+	{
+		.name = "deny",
+		.write = 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 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;
+}