1 files changed, 61 insertions, 26 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 44dfc415a379..842c254396db 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -42,7 +42,10 @@ struct dev_exception_item {
 struct dev_cgroup {
         struct cgroup_subsys_state css;
         struct list_head exceptions;
-        bool deny_all;
+        enum {
+                DEVCG_DEFAULT_ALLOW,
+                DEVCG_DEFAULT_DENY,
+        } behavior;
 };
 
 static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -182,13 +185,13 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup *cgroup)
         parent_cgroup = cgroup->parent;
 
         if (parent_cgroup == NULL)
-                dev_cgroup->deny_all = false;
+                dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
         else {
                 parent_dev_cgroup = cgroup_to_devcgroup(parent_cgroup);
                 mutex_lock(&devcgroup_mutex);
                 ret = dev_exceptions_copy(&dev_cgroup->exceptions,
                                           &parent_dev_cgroup->exceptions);
-                dev_cgroup->deny_all = parent_dev_cgroup->deny_all;
+                dev_cgroup->behavior = parent_dev_cgroup->behavior;
                 mutex_unlock(&devcgroup_mutex);
                 if (ret) {
                         kfree(dev_cgroup);
@@ -260,7 +263,7 @@ static int devcgroup_seq_read(struct cgroup *cgroup, struct cftype *cft,
          * - List the exceptions in case the default policy is to deny
          * This way, the file remains as a "whitelist of devices"
          */
-        if (devcgroup->deny_all == false) {
+        if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
                 set_access(acc, ACC_MASK);
                 set_majmin(maj, ~0);
                 set_majmin(min, ~0);
@@ -314,12 +317,12 @@ static int may_access(struct dev_cgroup *dev_cgroup,
          * In two cases we'll consider this new exception valid:
          * - the dev cgroup has its default policy to allow + exception list:
          *   the new exception should *not* match any of the exceptions
-         *   (!deny_all, !match)
+         *   (behavior == DEVCG_DEFAULT_ALLOW, !match)
          * - the dev cgroup has its default policy to deny + exception list:
          *   the new exception *should* match the exceptions
-         *   (deny_all, match)
+         *   (behavior == DEVCG_DEFAULT_DENY, match)
          */
-        if (dev_cgroup->deny_all == match)
+        if ((dev_cgroup->behavior == DEVCG_DEFAULT_DENY) == match)
                 return 1;
         return 0;
 }
@@ -341,6 +344,17 @@ static int parent_has_perm(struct dev_cgroup *childcg,
         return may_access(parent, ex);
 }
 
+/**
+ * may_allow_all - checks if it's possible to change the behavior to
+ *                 allow based on parent's rules.
+ * @parent: device cgroup's parent
+ * returns: != 0 in case it's allowed, 0 otherwise
+ */
+static inline int may_allow_all(struct dev_cgroup *parent)
+{
+        return parent->behavior == DEVCG_DEFAULT_ALLOW;
+}
+
 /*
  * Modify the exception list using allow/deny rules.
  * CAP_SYS_ADMIN is needed for this.  It's at least separate from CAP_MKNOD
@@ -358,9 +372,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                                    int filetype, const char *buffer)
 {
         const char *b;
-        char *endp;
-        int count;
+        char temp[12];          /* 11 + 1 characters needed for a u32 */
+        int count, rc;
         struct dev_exception_item ex;
+        struct cgroup *p = devcgroup->css.cgroup;
+        struct dev_cgroup *parent = cgroup_to_devcgroup(p->parent);
 
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;
@@ -372,14 +388,18 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
         case 'a':
                 switch (filetype) {
                 case DEVCG_ALLOW:
-                        if (!parent_has_perm(devcgroup, &ex))
+                        if (!may_allow_all(parent))
                                 return -EPERM;
                         dev_exception_clean(devcgroup);
-                        devcgroup->deny_all = false;
+                        rc = dev_exceptions_copy(&devcgroup->exceptions,
+                                                 &parent->exceptions);
+                        if (rc)
+                                return rc;
+                        devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
                         break;
                 case DEVCG_DENY:
                         dev_exception_clean(devcgroup);
-                        devcgroup->deny_all = true;
+                        devcgroup->behavior = DEVCG_DEFAULT_DENY;
                         break;
                 default:
                         return -EINVAL;
@@ -402,8 +422,16 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                 ex.major = ~0;
                 b++;
         } else if (isdigit(*b)) {
-                ex.major = simple_strtoul(b, &endp, 10);
-                b = endp;
+                memset(temp, 0, sizeof(temp));
+                for (count = 0; count < sizeof(temp) - 1; count++) {
+                        temp[count] = *b;
+                        b++;
+                        if (!isdigit(*b))
+                                break;
+                }
+                rc = kstrtou32(temp, 10, &ex.major);
+                if (rc)
+                        return -EINVAL;
         } else {
                 return -EINVAL;
         }
@@ -416,8 +444,16 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                 ex.minor = ~0;
                 b++;
         } else if (isdigit(*b)) {
-                ex.minor = simple_strtoul(b, &endp, 10);
-                b = endp;
+                memset(temp, 0, sizeof(temp));
+                for (count = 0; count < sizeof(temp) - 1; count++) {
+                        temp[count] = *b;
+                        b++;
+                        if (!isdigit(*b))
+                                break;
+                }
+                rc = kstrtou32(temp, 10, &ex.minor);
+                if (rc)
+                        return -EINVAL;
         } else {
                 return -EINVAL;
         }
@@ -452,7 +488,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                  * an matching exception instead. And be silent about it: we
                  * don't want to break compatibility
                  */
-                if (devcgroup->deny_all == false) {
+                if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
                         dev_exception_rm(devcgroup, &ex);
                         return 0;
                 }
@@ -463,7 +499,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
                  * an matching exception instead. And be silent about it: we
                  * don't want to break compatibility
                  */
-                if (devcgroup->deny_all == true) {
+                if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
                         dev_exception_rm(devcgroup, &ex);
                         return 0;
                 }
@@ -533,10 +569,10 @@ struct cgroup_subsys devices_subsys = {
  *
  * returns 0 on success, -EPERM case the operation is not permitted
  */
-static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
-                                        short type, u32 major, u32 minor,
+static int __devcgroup_check_permission(short type, u32 major, u32 minor,
                                         short access)
 {
+        struct dev_cgroup *dev_cgroup;
         struct dev_exception_item ex;
         int rc;
 
@@ -547,6 +583,7 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
         ex.access = access;
 
         rcu_read_lock();
+        dev_cgroup = task_devcgroup(current);
         rc = may_access(dev_cgroup, &ex);
         rcu_read_unlock();
 
@@ -558,7 +595,6 @@ static int __devcgroup_check_permission(struct dev_cgroup *dev_cgroup,
 
 int __devcgroup_inode_permission(struct inode *inode, int mask)
 {
-        struct dev_cgroup *dev_cgroup = task_devcgroup(current);
         short type, access = 0;
 
         if (S_ISBLK(inode->i_mode))
@@ -570,13 +606,12 @@ int __devcgroup_inode_permission(struct inode *inode, int mask)
         if (mask & MAY_READ)
                 access |= ACC_READ;
 
-        return __devcgroup_check_permission(dev_cgroup, type, imajor(inode),
-                                            iminor(inode), access);
+        return __devcgroup_check_permission(type, imajor(inode), iminor(inode),
+                        access);
 }
 
 int devcgroup_inode_mknod(int mode, dev_t dev)
 {
-        struct dev_cgroup *dev_cgroup = task_devcgroup(current);
         short type;
 
         if (!S_ISBLK(mode) && !S_ISCHR(mode))
@@ -587,7 +622,7 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
         else
                 type = DEV_CHAR;
 
-        return __devcgroup_check_permission(dev_cgroup, type, MAJOR(dev),
-                                            MINOR(dev), ACC_MKNOD);
+        return __devcgroup_check_permission(type, MAJOR(dev), MINOR(dev),
+                        ACC_MKNOD);
 
 }