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-rw-r--r--security/device_cgroup.c546
1 files changed, 546 insertions, 0 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
new file mode 100644
index 00000000..1be68269
--- /dev/null
+++ b/security/device_cgroup.c
@@ -0,0 +1,546 @@
+/*
+ * 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/slab.h>
+#include <linux/rcupdate.h>
+#include <linux/mutex.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 */
+
+static DEFINE_MUTEX(devcgroup_mutex);
+
+/*
+ * whitelist locking rules:
+ * hold devcgroup_mutex 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 devcgroup_mutex
+ */
+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 devcgroup_mutex
+ */
+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 devcgroup_mutex
+ */
+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);
+ mutex_lock(&devcgroup_mutex);
+ ret = dev_whitelist_copy(&dev_cgroup->whitelist,
+ &parent_dev_cgroup->whitelist);
+ mutex_unlock(&devcgroup_mutex);
+ 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 devcgroup_mutex 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;
+
+ mutex_lock(&devcgroup_mutex);
+ retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
+ cft->private, buffer);
+ mutex_unlock(&devcgroup_mutex);
+ 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;
+
+ rcu_read_lock();
+
+ dev_cgroup = task_devcgroup(current);
+
+ list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
+ if (wh->type & DEV_ALL)
+ goto found;
+ 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;
+
+ if ((mask & MAY_WRITE) && !(wh->access & ACC_WRITE))
+ continue;
+ if ((mask & MAY_READ) && !(wh->access & ACC_READ))
+ continue;
+found:
+ 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 found;
+ 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;
+
+ if (!(wh->access & ACC_MKNOD))
+ continue;
+found:
+ rcu_read_unlock();
+ return 0;
+ }
+
+ rcu_read_unlock();
+
+ return -EPERM;
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-01 02:51:53 +0000