1 files changed, 68 insertions, 90 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index ddd92cec78ed..7bd296cca041 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -41,6 +41,7 @@ struct dev_whitelist_item {
         short type;
         short access;
         struct list_head list;
+        struct rcu_head rcu;
 };
 
 struct dev_cgroup {
@@ -59,6 +60,11 @@ 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,
@@ -128,11 +134,19 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
         }
 
         if (whcopy != NULL)
-                list_add_tail(&whcopy->list, &dev_cgroup->whitelist);
+                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
@@ -156,8 +170,8 @@ static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
 remove:
                 walk->access &= ~wh->access;
                 if (!walk->access) {
-                        list_del(&walk->list);
-                        kfree(walk);
+                        list_del_rcu(&walk->list);
+                        call_rcu(&walk->rcu, whitelist_item_free);
                 }
         }
         spin_unlock(&dev_cgroup->lock);
@@ -188,7 +202,7 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
                 }
                 wh->minor = wh->major = ~0;
                 wh->type = DEV_ALL;
-                wh->access = ACC_MKNOD | ACC_READ | ACC_WRITE;
+                wh->access = ACC_MASK;
                 list_add(&wh->list, &dev_cgroup->whitelist);
         } else {
                 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
@@ -250,11 +264,10 @@ static char type_to_char(short type)
 
 static void set_majmin(char *str, unsigned m)
 {
-        memset(str, 0, MAJMINLEN);
         if (m == ~0)
-                sprintf(str, "*");
+                strcpy(str, "*");
         else
-                snprintf(str, MAJMINLEN, "%u", m);
+                sprintf(str, "%u", m);
 }
 
 static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
@@ -264,15 +277,15 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
         struct dev_whitelist_item *wh;
         char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
 
-        spin_lock(&devcgroup->lock);
-        list_for_each_entry(wh, &devcgroup->whitelist, list) {
+        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);
         }
-        spin_unlock(&devcgroup->lock);
+        rcu_read_unlock();
 
         return 0;
 }
@@ -312,10 +325,10 @@ static int may_access_whitelist(struct dev_cgroup *c,
  * 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,
+static int parent_has_perm(struct dev_cgroup *childcg,
                                   struct dev_whitelist_item *wh)
 {
-        struct cgroup *pcg = childcg->parent;
+        struct cgroup *pcg = childcg->css.cgroup->parent;
         struct dev_cgroup *parent;
         int ret;
 
@@ -341,39 +354,19 @@ static int parent_has_perm(struct cgroup *childcg,
  * 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)
+static int devcgroup_update_access(struct dev_cgroup *devcgroup,
+                                   int filetype, const char *buffer)
 {
-        struct cgroup *cur_cgroup;
-        struct dev_cgroup *devcgroup, *cur_devcgroup;
-        int filetype = cft->private;
-        char *buffer, *b;
+        struct dev_cgroup *cur_devcgroup;
+        const char *b;
+        char *endp;
         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;
-        }
+        cur_devcgroup = task_devcgroup(current);
 
         memset(&wh, 0, sizeof(wh));
         b = buffer;
@@ -392,32 +385,23 @@ static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
                 wh.type = DEV_CHAR;
                 break;
         default:
-                retval = -EINVAL;
-                goto out2;
+                return -EINVAL;
         }
         b++;
-        if (!isspace(*b)) {
-                retval = -EINVAL;
-                goto out2;
-        }
+        if (!isspace(*b))
+                return -EINVAL;
         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++;
-                }
+                wh.major = simple_strtoul(b, &endp, 10);
+                b = endp;
         } else {
-                retval = -EINVAL;
-                goto out2;
-        }
-        if (*b != ':') {
-                retval = -EINVAL;
-                goto out2;
+                return -EINVAL;
         }
+        if (*b != ':')
+                return -EINVAL;
         b++;
 
         /* read minor */
@@ -425,19 +409,13 @@ static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
                 wh.minor = ~0;
                 b++;
         } else if (isdigit(*b)) {
-                wh.minor = 0;
-                while (isdigit(*b)) {
-                        wh.minor = wh.minor*10+(*b-'0');
-                        b++;
-                }
+                wh.minor = simple_strtoul(b, &endp, 10);
+                b = endp;
         } else {
-                retval = -EINVAL;
-                goto out2;
-        }
-        if (!isspace(*b)) {
-                retval = -EINVAL;
-                goto out2;
+                return -EINVAL;
         }
+        if (!isspace(*b))
+                return -EINVAL;
         for (b++, count = 0; count < 3; count++, b++) {
                 switch (*b) {
                 case 'r':
@@ -454,8 +432,7 @@ static ssize_t devcgroup_access_write(struct cgroup *cgroup, struct cftype *cft,
                         count = 3;
                         break;
                 default:
-                        retval = -EINVAL;
-                        goto out2;
+                        return -EINVAL;
                 }
         }
 
@@ -463,38 +440,39 @@ handle:
         retval = 0;
         switch (filetype) {
         case DEVCG_ALLOW:
-                if (!parent_has_perm(cgroup, &wh))
-                        retval = -EPERM;
-                else
-                        retval = dev_whitelist_add(devcgroup, &wh);
-                break;
+                if (!parent_has_perm(devcgroup, &wh))
+                        return -EPERM;
+                return dev_whitelist_add(devcgroup, &wh);
         case DEVCG_DENY:
                 dev_whitelist_rm(devcgroup, &wh);
                 break;
         default:
-                retval = -EINVAL;
-                goto out2;
+                return -EINVAL;
         }
+        return 0;
+}
 
-        if (retval == 0)
-                retval = nbytes;
-
-out2:
+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();
-out1:
-        kfree(buffer);
         return retval;
 }
 
 static struct cftype dev_cgroup_files[] = {
         {
                 .name = "allow",
-                .write  = devcgroup_access_write,
+                .write_string  = devcgroup_access_write,
                 .private = DEVCG_ALLOW,
         },
         {
                 .name = "deny",
-                .write = devcgroup_access_write,
+                .write_string = devcgroup_access_write,
                 .private = DEVCG_DENY,
         },
         {
@@ -535,8 +513,8 @@ int devcgroup_inode_permission(struct inode *inode, int mask)
         if (!dev_cgroup)
                 return 0;
 
-        spin_lock(&dev_cgroup->lock);
-        list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
+        rcu_read_lock();
+        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))
@@ -552,10 +530,10 @@ acc_check:
                         continue;
                 if ((mask & MAY_READ) && !(wh->access & ACC_READ))
                         continue;
-                spin_unlock(&dev_cgroup->lock);
+                rcu_read_unlock();
                 return 0;
         }
-        spin_unlock(&dev_cgroup->lock);
+        rcu_read_unlock();
 
         return -EPERM;
 }
@@ -570,7 +548,7 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
         if (!dev_cgroup)
                 return 0;
 
-        spin_lock(&dev_cgroup->lock);
+        rcu_read_lock();
         list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
                 if (wh->type & DEV_ALL)
                         goto acc_check;
@@ -585,9 +563,9 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
 acc_check:
                 if (!(wh->access & ACC_MKNOD))
                         continue;
-                spin_unlock(&dev_cgroup->lock);
+                rcu_read_unlock();
                 return 0;
         }
-        spin_unlock(&dev_cgroup->lock);
+        rcu_read_unlock();
         return -EPERM;
 }