Merge git://git.samba.org/sfrench/cifs-2.6
[linux-2.6.git] / security / device_cgroup.c
index 7bd296c..8b5b5d8 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * dev_cgroup.c - device cgroup subsystem
+ * device_cgroup.c - device cgroup subsystem
  *
  * Copyright 2007 IBM Corp
  */
@@ -10,6 +10,9 @@
 #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 DEV_CHAR  2
 #define DEV_ALL   4  /* this represents all devices */
 
+static DEFINE_MUTEX(devcgroup_mutex);
+
 /*
  * 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.
+ * hold devcgroup_mutex for update/read.
+ * hold rcu_read_lock() for read.
  */
 
 struct dev_whitelist_item {
@@ -47,7 +42,6 @@ struct dev_whitelist_item {
 struct dev_cgroup {
        struct cgroup_subsys_state css;
        struct list_head whitelist;
-       spinlock_t lock;
 };
 
 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -68,29 +62,26 @@ static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
 struct cgroup_subsys devices_subsys;
 
 static int devcgroup_can_attach(struct cgroup_subsys *ss,
-               struct cgroup *new_cgroup, struct task_struct *task)
+                       struct cgroup *new_cgrp, struct cgroup_taskset *set)
 {
-       if (current != task && !capable(CAP_SYS_ADMIN))
-                       return -EPERM;
+       struct task_struct *task = cgroup_taskset_first(set);
 
+       if (current != task && !capable(CAP_SYS_ADMIN))
+               return -EPERM;
        return 0;
 }
 
 /*
- * called under cgroup_lock()
+ * 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 = kmalloc(sizeof(*wh), GFP_KERNEL);
+               new = kmemdup(wh, 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);
        }
 
@@ -106,20 +97,17 @@ free_and_exit:
 
 /* 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
+ * 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 = kmalloc(sizeof(*whcopy), GFP_KERNEL);
+       whcopy = kmemdup(wh, sizeof(*wh), GFP_KERNEL);
        if (!whcopy)
                return -ENOMEM;
 
-       memcpy(whcopy, wh, sizeof(*whcopy));
-       spin_lock(&dev_cgroup->lock);
        list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
                if (walk->type != wh->type)
                        continue;
@@ -135,28 +123,17 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
 
        if (whcopy != NULL)
                list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
-       spin_unlock(&dev_cgroup->lock);
        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()
- * since the list is visible to other tasks, we need the spinlock also
+ * 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;
 
-       spin_lock(&dev_cgroup->lock);
        list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
                if (walk->type == DEV_ALL)
                        goto remove;
@@ -171,10 +148,9 @@ remove:
                walk->access &= ~wh->access;
                if (!walk->access) {
                        list_del_rcu(&walk->list);
-                       call_rcu(&walk->rcu, whitelist_item_free);
+                       kfree_rcu(walk, rcu);
                }
        }
-       spin_unlock(&dev_cgroup->lock);
 }
 
 /*
@@ -206,15 +182,16 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
                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);
                }
        }
 
-       spin_lock_init(&dev_cgroup->lock);
        return &dev_cgroup->css;
 }
 
@@ -295,7 +272,7 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
  * 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
+ * call with devcgroup_mutex held
  */
 static int may_access_whitelist(struct dev_cgroup *c,
                                       struct dev_whitelist_item *refwh)
@@ -330,15 +307,11 @@ static int parent_has_perm(struct dev_cgroup *childcg,
 {
        struct cgroup *pcg = childcg->css.cgroup->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;
+       return may_access_whitelist(parent, wh);
 }
 
 /*
@@ -357,17 +330,14 @@ static int parent_has_perm(struct dev_cgroup *childcg,
 static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                                   int filetype, const char *buffer)
 {
-       struct dev_cgroup *cur_devcgroup;
        const char *b;
        char *endp;
-       int retval = 0, count;
+       int count;
        struct dev_whitelist_item wh;
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
 
-       cur_devcgroup = task_devcgroup(current);
-
        memset(&wh, 0, sizeof(wh));
        b = buffer;
 
@@ -437,7 +407,6 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
        }
 
 handle:
-       retval = 0;
        switch (filetype) {
        case DEVCG_ALLOW:
                if (!parent_has_perm(devcgroup, &wh))
@@ -456,11 +425,11 @@ static int devcgroup_access_write(struct cgroup *cgrp, struct cftype *cft,
                                  const char *buffer)
 {
        int retval;
-       if (!cgroup_lock_live_group(cgrp))
-               return -ENODEV;
+
+       mutex_lock(&devcgroup_mutex);
        retval = devcgroup_update_access(cgroup_to_devcgroup(cgrp),
                                         cft->private, buffer);
-       cgroup_unlock();
+       mutex_unlock(&devcgroup_mutex);
        return retval;
 }
 
@@ -493,30 +462,23 @@ struct cgroup_subsys devices_subsys = {
        .name = "devices",
        .can_attach = devcgroup_can_attach,
        .create = devcgroup_create,
-       .destroy  = devcgroup_destroy,
+       .destroy = devcgroup_destroy,
        .populate = devcgroup_populate,
        .subsys_id = devices_subsys_id,
 };
 
-int devcgroup_inode_permission(struct inode *inode, int mask)
+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;
-       dev_cgroup = css_to_devcgroup(task_subsys_state(current,
-                               devices_subsys_id));
-       if (!dev_cgroup)
-               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;
+                       goto found;
                if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode))
                        continue;
                if ((wh->type & DEV_CHAR) && !S_ISCHR(inode->i_mode))
@@ -525,14 +487,16 @@ int devcgroup_inode_permission(struct inode *inode, int mask)
                        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;
+found:
                rcu_read_unlock();
                return 0;
        }
+
        rcu_read_unlock();
 
        return -EPERM;
@@ -543,15 +507,16 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
        struct dev_cgroup *dev_cgroup;
        struct dev_whitelist_item *wh;
 
-       dev_cgroup = css_to_devcgroup(task_subsys_state(current,
-                               devices_subsys_id));
-       if (!dev_cgroup)
+       if (!S_ISBLK(mode) && !S_ISCHR(mode))
                return 0;
 
        rcu_read_lock();
-       list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
+
+       dev_cgroup = task_devcgroup(current);
+
+       list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
                if (wh->type & DEV_ALL)
-                       goto acc_check;
+                       goto found;
                if ((wh->type & DEV_BLOCK) && !S_ISBLK(mode))
                        continue;
                if ((wh->type & DEV_CHAR) && !S_ISCHR(mode))
@@ -560,12 +525,15 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
                        continue;
                if (wh->minor != ~0 && wh->minor != MINOR(dev))
                        continue;
-acc_check:
+
                if (!(wh->access & ACC_MKNOD))
                        continue;
+found:
                rcu_read_unlock();
                return 0;
        }
+
        rcu_read_unlock();
+
        return -EPERM;
 }