ANDROID: sdcardfs: add support for user permission isolation
authorDaniel Rosenberg <drosen@google.com>
Sun, 22 Jan 2017 23:32:49 +0000 (15:32 -0800)
committerAmit Pundir <amit.pundir@linaro.org>
Fri, 3 Feb 2017 09:35:18 +0000 (15:05 +0530)
This allows you to hide the existence of a package from
a user by adding them to an exclude list. If a user
creates that package's folder and is on the exclude list,
they will not see that package's id.

Bug: 34542611
Change-Id: I9eb82e0bf2457d7eb81ee56153b9c7d2f6646323
Signed-off-by: Daniel Rosenberg <drosen@google.com>
fs/sdcardfs/derived_perm.c
fs/sdcardfs/packagelist.c
fs/sdcardfs/sdcardfs.h

index 0c1a91f70b40bfc2e16cb3e401a97faaffa03f90..8e3baee4a2d905170979032ec870ca693dfd34f6 100644 (file)
@@ -103,7 +103,7 @@ void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, st
                case PERM_ANDROID_OBB:
                case PERM_ANDROID_MEDIA:
                        appid = get_appid(newdentry->d_name.name);
-                       if (appid != 0) {
+                       if (appid != 0 && !is_excluded(newdentry->d_name.name, parent_info->userid)) {
                                info->d_uid = multiuser_get_uid(parent_info->userid, appid);
                        }
                        set_top(info, &info->vfs_inode);
@@ -116,8 +116,10 @@ void get_derived_permission(struct dentry *parent, struct dentry *dentry)
        get_derived_permission_new(parent, dentry, dentry);
 }
 
-static int descendant_may_need_fixup(perm_t perm) {
-       if (perm == PERM_PRE_ROOT || perm == PERM_ROOT || perm == PERM_ANDROID)
+static int descendant_may_need_fixup(struct sdcardfs_inode_info *info, struct limit_search *limit) {
+       if (info->perm == PERM_ROOT)
+               return (limit->flags & BY_USERID)?info->userid == limit->userid:1;
+       if (info->perm == PERM_PRE_ROOT || info->perm == PERM_ANDROID)
                return 1;
        return 0;
 }
@@ -129,7 +131,7 @@ static int needs_fixup(perm_t perm) {
        return 0;
 }
 
-void fixup_perms_recursive(struct dentry *dentry, const char* name, size_t len) {
+void fixup_perms_recursive(struct dentry *dentry, struct limit_search *limit) {
        struct dentry *child;
        struct sdcardfs_inode_info *info;
        if (!dget(dentry))
@@ -143,22 +145,22 @@ void fixup_perms_recursive(struct dentry *dentry, const char* name, size_t len)
        if (needs_fixup(info->perm)) {
                spin_lock(&dentry->d_lock);
                list_for_each_entry(child, &dentry->d_subdirs, d_child) {
-                               dget(child);
-                               if (!strncasecmp(child->d_name.name, name, len)) {
-                                       if (d_inode(child)) {
-                                               get_derived_permission(dentry, child);
-                                               fixup_tmp_permissions(d_inode(child));
-                                               dput(child);
-                                               break;
-                                       }
+                       dget(child);
+                       if (!(limit->flags & BY_NAME) || !strncasecmp(child->d_name.name, limit->name, limit->length)) {
+                               if (d_inode(child)) {
+                                       get_derived_permission(dentry, child);
+                                       fixup_tmp_permissions(d_inode(child));
+                                       dput(child);
+                                       break;
                                }
-                               dput(child);
+                       }
+                       dput(child);
                }
                spin_unlock(&dentry->d_lock);
-       } else  if (descendant_may_need_fixup(info->perm)) {
+       } else  if (descendant_may_need_fixup(info, limit)) {
                spin_lock(&dentry->d_lock);
                list_for_each_entry(child, &dentry->d_subdirs, d_child) {
-                               fixup_perms_recursive(child, name, len);
+                               fixup_perms_recursive(child, limit);
                }
                spin_unlock(&dentry->d_lock);
        }
index 0b3fb50b1fe46e7df86a999b2bf63a06b41cb465..6eb73ddc2cebe878e3e409e4e184940862b3e01b 100644 (file)
 
 struct hashtable_entry {
        struct hlist_node hlist;
+       struct hlist_node dlist; /* for deletion cleanup */
        const char *key;
        atomic_t value;
 };
 
 static DEFINE_HASHTABLE(package_to_appid, 8);
+static DEFINE_HASHTABLE(package_to_userid, 8);
 
 static struct kmem_cache *hashtable_entry_cachep;
 
@@ -69,6 +71,22 @@ appid_t get_appid(const char *app_name)
        return 0;
 }
 
+appid_t is_excluded(const char *app_name, userid_t user)
+{
+       struct hashtable_entry *hash_cur;
+       unsigned int hash = str_hash(app_name);
+
+       rcu_read_lock();
+       hash_for_each_possible_rcu(package_to_userid, hash_cur, hlist, hash) {
+               if (atomic_read(&hash_cur->value) == user && !strcasecmp(app_name, hash_cur->key)) {
+                       rcu_read_unlock();
+                       return 1;
+               }
+       }
+       rcu_read_unlock();
+       return 0;
+}
+
 /* Kernel has already enforced everything we returned through
  * derive_permissions_locked(), so this is used to lock down access
  * even further, such as enforcing that apps hold sdcard_rw. */
@@ -124,7 +142,7 @@ static struct hashtable_entry *alloc_packagelist_entry(const char *key,
        return ret;
 }
 
-static int insert_packagelist_entry_locked(const char *key, appid_t value)
+static int insert_packagelist_appid_entry_locked(const char *key, appid_t value)
 {
        struct hashtable_entry *hash_cur;
        struct hashtable_entry *new_entry;
@@ -143,18 +161,64 @@ static int insert_packagelist_entry_locked(const char *key, appid_t value)
        return 0;
 }
 
-static void fixup_perms(struct super_block *sb, const char *key) {
-       if (sb && sb->s_magic == SDCARDFS_SUPER_MAGIC) {
-               fixup_perms_recursive(sb->s_root, key, strlen(key));
+static int insert_userid_exclude_entry_locked(const char *key, userid_t value)
+{
+       struct hashtable_entry *hash_cur;
+       struct hashtable_entry *new_entry;
+       unsigned int hash = str_hash(key);
+
+       /* Only insert if not already present */
+       hash_for_each_possible_rcu(package_to_userid, hash_cur, hlist, hash) {
+               if (atomic_read(&hash_cur->value) == value && !strcasecmp(key, hash_cur->key))
+                       return 0;
+       }
+       new_entry = alloc_packagelist_entry(key, value);
+       if (!new_entry)
+               return -ENOMEM;
+       hash_add_rcu(package_to_userid, &new_entry->hlist, hash);
+       return 0;
+}
+
+static void fixup_all_perms_name(const char *key)
+{
+       struct sdcardfs_sb_info *sbinfo;
+       struct limit_search limit = {
+               .flags = BY_NAME,
+               .name = key,
+               .length = strlen(key),
+       };
+       list_for_each_entry(sbinfo, &sdcardfs_super_list, list) {
+               if (sbinfo_has_sdcard_magic(sbinfo))
+                       fixup_perms_recursive(sbinfo->sb->s_root, &limit);
        }
 }
 
-static void fixup_all_perms(const char *key)
+static void fixup_all_perms_name_userid(const char *key, userid_t userid)
 {
        struct sdcardfs_sb_info *sbinfo;
-       list_for_each_entry(sbinfo, &sdcardfs_super_list, list)
-               if (sbinfo)
-                       fixup_perms(sbinfo->sb, key);
+       struct limit_search limit = {
+               .flags = BY_NAME | BY_USERID,
+               .name = key,
+               .length = strlen(key),
+               .userid = userid,
+       };
+       list_for_each_entry(sbinfo, &sdcardfs_super_list, list) {
+               if (sbinfo_has_sdcard_magic(sbinfo))
+                       fixup_perms_recursive(sbinfo->sb->s_root, &limit);
+       }
+}
+
+static void fixup_all_perms_userid(userid_t userid)
+{
+       struct sdcardfs_sb_info *sbinfo;
+       struct limit_search limit = {
+               .flags = BY_USERID,
+               .userid = userid,
+       };
+       list_for_each_entry(sbinfo, &sdcardfs_super_list, list) {
+               if (sbinfo_has_sdcard_magic(sbinfo))
+                       fixup_perms_recursive(sbinfo->sb->s_root, &limit);
+       }
 }
 
 static int insert_packagelist_entry(const char *key, appid_t value)
@@ -162,9 +226,22 @@ static int insert_packagelist_entry(const char *key, appid_t value)
        int err;
 
        mutex_lock(&sdcardfs_super_list_lock);
-       err = insert_packagelist_entry_locked(key, value);
+       err = insert_packagelist_appid_entry_locked(key, value);
        if (!err)
-               fixup_all_perms(key);
+               fixup_all_perms_name(key);
+       mutex_unlock(&sdcardfs_super_list_lock);
+
+       return err;
+}
+
+static int insert_userid_exclude_entry(const char *key, userid_t value)
+{
+       int err;
+
+       mutex_lock(&sdcardfs_super_list_lock);
+       err = insert_userid_exclude_entry_locked(key, value);
+       if (!err)
+               fixup_all_perms_name_userid(key, value);
        mutex_unlock(&sdcardfs_super_list_lock);
 
        return err;
@@ -173,7 +250,7 @@ static int insert_packagelist_entry(const char *key, appid_t value)
 static void free_packagelist_entry(struct hashtable_entry *entry)
 {
        kfree(entry->key);
-       hash_del_rcu(&entry->hlist);
+       hash_del_rcu(&entry->dlist);
        kmem_cache_free(hashtable_entry_cachep, entry);
 }
 
@@ -181,22 +258,84 @@ static void remove_packagelist_entry_locked(const char *key)
 {
        struct hashtable_entry *hash_cur;
        unsigned int hash = str_hash(key);
+       struct hlist_node *h_t;
+       HLIST_HEAD(free_list);
 
+       hash_for_each_possible_rcu(package_to_userid, hash_cur, hlist, hash) {
+               if (!strcasecmp(key, hash_cur->key)) {
+                       hash_del_rcu(&hash_cur->hlist);
+                       hlist_add_head(&hash_cur->dlist, &free_list);
+               }
+       }
        hash_for_each_possible_rcu(package_to_appid, hash_cur, hlist, hash) {
                if (!strcasecmp(key, hash_cur->key)) {
                        hash_del_rcu(&hash_cur->hlist);
-                       synchronize_rcu();
-                       free_packagelist_entry(hash_cur);
-                       return;
+                       hlist_add_head(&hash_cur->dlist, &free_list);
+                       break;
                }
        }
+       synchronize_rcu();
+       hlist_for_each_entry_safe(hash_cur, h_t, &free_list, dlist)
+               free_packagelist_entry(hash_cur);
 }
 
 static void remove_packagelist_entry(const char *key)
 {
        mutex_lock(&sdcardfs_super_list_lock);
        remove_packagelist_entry_locked(key);
-       fixup_all_perms(key);
+       fixup_all_perms_name(key);
+       mutex_unlock(&sdcardfs_super_list_lock);
+       return;
+}
+
+static void remove_userid_all_entry_locked(userid_t userid)
+{
+       struct hashtable_entry *hash_cur;
+       struct hlist_node *h_t;
+       HLIST_HEAD(free_list);
+       int i;
+
+       hash_for_each_rcu(package_to_userid, i, hash_cur, hlist) {
+               if (atomic_read(&hash_cur->value) == userid) {
+                       hash_del_rcu(&hash_cur->hlist);
+                       hlist_add_head(&hash_cur->dlist, &free_list);
+               }
+       }
+       synchronize_rcu();
+       hlist_for_each_entry_safe(hash_cur, h_t, &free_list, dlist) {
+               free_packagelist_entry(hash_cur);
+       }
+}
+
+static void remove_userid_all_entry(userid_t userid)
+{
+       mutex_lock(&sdcardfs_super_list_lock);
+       remove_userid_all_entry_locked(userid);
+       fixup_all_perms_userid(userid);
+       mutex_unlock(&sdcardfs_super_list_lock);
+       return;
+}
+
+static void remove_userid_exclude_entry_locked(const char *key, userid_t userid)
+{
+       struct hashtable_entry *hash_cur;
+       unsigned int hash = str_hash(key);
+
+       hash_for_each_possible_rcu(package_to_userid, hash_cur, hlist, hash) {
+               if (!strcasecmp(key, hash_cur->key) && atomic_read(&hash_cur->value) == userid) {
+                       hash_del_rcu(&hash_cur->hlist);
+                       synchronize_rcu();
+                       free_packagelist_entry(hash_cur);
+                       break;
+               }
+       }
+}
+
+static void remove_userid_exclude_entry(const char *key, userid_t userid)
+{
+       mutex_lock(&sdcardfs_super_list_lock);
+       remove_userid_exclude_entry_locked(key, userid);
+       fixup_all_perms_name_userid(key, userid);
        mutex_unlock(&sdcardfs_super_list_lock);
        return;
 }
@@ -210,16 +349,44 @@ static void packagelist_destroy(void)
        mutex_lock(&sdcardfs_super_list_lock);
        hash_for_each_rcu(package_to_appid, i, hash_cur, hlist) {
                hash_del_rcu(&hash_cur->hlist);
-               hlist_add_head(&hash_cur->hlist, &free_list);
-
+               hlist_add_head(&hash_cur->dlist, &free_list);
+       }
+       hash_for_each_rcu(package_to_userid, i, hash_cur, hlist) {
+               hash_del_rcu(&hash_cur->hlist);
+               hlist_add_head(&hash_cur->dlist, &free_list);
        }
        synchronize_rcu();
-       hlist_for_each_entry_safe(hash_cur, h_t, &free_list, hlist)
+       hlist_for_each_entry_safe(hash_cur, h_t, &free_list, dlist)
                free_packagelist_entry(hash_cur);
        mutex_unlock(&sdcardfs_super_list_lock);
        printk(KERN_INFO "sdcardfs: destroyed packagelist pkgld\n");
 }
 
+#define SDCARDFS_CONFIGFS_ATTR(_pfx, _name)                    \
+static struct configfs_attribute _pfx##attr_##_name = {        \
+       .ca_name        = __stringify(_name),           \
+       .ca_mode        = S_IRUGO | S_IWUGO,            \
+       .ca_owner       = THIS_MODULE,                  \
+       .show           = _pfx##_name##_show,           \
+       .store          = _pfx##_name##_store,          \
+}
+
+#define SDCARDFS_CONFIGFS_ATTR_RO(_pfx, _name)                 \
+static struct configfs_attribute _pfx##attr_##_name = {        \
+       .ca_name        = __stringify(_name),           \
+       .ca_mode        = S_IRUGO,                      \
+       .ca_owner       = THIS_MODULE,                  \
+       .show           = _pfx##_name##_show,           \
+}
+
+#define SDCARDFS_CONFIGFS_ATTR_WO(_pfx, _name)                 \
+static struct configfs_attribute _pfx##attr_##_name = {        \
+       .ca_name        = __stringify(_name),           \
+       .ca_mode        = S_IWUGO,                      \
+       .ca_owner       = THIS_MODULE,                  \
+       .store          = _pfx##_name##_store,          \
+}
+
 struct package_details {
        struct config_item item;
        const char *name;
@@ -253,6 +420,58 @@ static ssize_t package_details_appid_store(struct config_item *item,
        return count;
 }
 
+static ssize_t package_details_excluded_userids_show(struct config_item *item,
+                                     char *page)
+{
+       struct package_details *package_details = to_package_details(item);
+       struct hashtable_entry *hash_cur;
+       unsigned int hash = str_hash(package_details->name);
+       int count = 0;
+
+       rcu_read_lock();
+       hash_for_each_possible_rcu(package_to_userid, hash_cur, hlist, hash) {
+               if (!strcasecmp(package_details->name, hash_cur->key))
+                       count += scnprintf(page + count, PAGE_SIZE - count,
+                                       "%d ", atomic_read(&hash_cur->value));
+       }
+       rcu_read_unlock();
+       if (count)
+               count--;
+       count += scnprintf(page + count, PAGE_SIZE - count, "\n");
+       return count;
+}
+
+static ssize_t package_details_excluded_userids_store(struct config_item *item,
+                                      const char *page, size_t count)
+{
+       unsigned int tmp;
+       int ret;
+
+       ret = kstrtouint(page, 10, &tmp);
+       if (ret)
+               return ret;
+
+       ret = insert_userid_exclude_entry(to_package_details(item)->name, tmp);
+
+       if (ret)
+               return ret;
+
+       return count;
+}
+
+static ssize_t package_details_clear_userid_store(struct config_item *item,
+                                      const char *page, size_t count)
+{
+       unsigned int tmp;
+       int ret;
+
+       ret = kstrtouint(page, 10, &tmp);
+       if (ret)
+               return ret;
+       remove_userid_exclude_entry(to_package_details(item)->name, tmp);
+       return count;
+}
+
 static void package_details_release(struct config_item *item)
 {
        struct package_details *package_details = to_package_details(item);
@@ -262,10 +481,14 @@ static void package_details_release(struct config_item *item)
        kfree(package_details);
 }
 
-CONFIGFS_ATTR(package_details_, appid);
+SDCARDFS_CONFIGFS_ATTR(package_details_, appid);
+SDCARDFS_CONFIGFS_ATTR(package_details_, excluded_userids);
+SDCARDFS_CONFIGFS_ATTR_WO(package_details_, clear_userid);
 
 static struct configfs_attribute *package_details_attrs[] = {
        &package_details_attr_appid,
+       &package_details_attr_excluded_userids,
+       &package_details_attr_clear_userid,
        NULL,
 };
 
@@ -293,23 +516,33 @@ static struct config_item *packages_make_item(struct config_group *group, const
        }
 
        config_item_init_type_name(&package_details->item, name,
-                                  &package_appid_type);
+                                               &package_appid_type);
 
        return &package_details->item;
 }
 
 static ssize_t packages_list_show(struct config_item *item, char *page)
 {
-       struct hashtable_entry *hash_cur;
+       struct hashtable_entry *hash_cur_app;
+       struct hashtable_entry *hash_cur_user;
        int i;
        int count = 0, written = 0;
        const char errormsg[] = "<truncated>\n";
+       unsigned int hash;
 
        rcu_read_lock();
-       hash_for_each_rcu(package_to_appid, i, hash_cur, hlist) {
+       hash_for_each_rcu(package_to_appid, i, hash_cur_app, hlist) {
                written = scnprintf(page + count, PAGE_SIZE - sizeof(errormsg) - count, "%s %d\n",
-                                       (const char *)hash_cur->key, atomic_read(&hash_cur->value));
-               if (count + written == PAGE_SIZE - sizeof(errormsg)) {
+                                       hash_cur_app->key, atomic_read(&hash_cur_app->value));
+               hash = str_hash(hash_cur_app->key);
+               hash_for_each_possible_rcu(package_to_userid, hash_cur_user, hlist, hash) {
+                       if (!strcasecmp(hash_cur_app->key, hash_cur_user->key)) {
+                               written += scnprintf(page + count + written - 1,
+                                       PAGE_SIZE - sizeof(errormsg) - count - written + 1,
+                                       " %d\n",        atomic_read(&hash_cur_user->value)) - 1;
+                       }
+               }
+               if (count + written == PAGE_SIZE - sizeof(errormsg) - 1) {
                        count += scnprintf(page + count, PAGE_SIZE - count, errormsg);
                        break;
                }
@@ -320,6 +553,19 @@ static ssize_t packages_list_show(struct config_item *item, char *page)
        return count;
 }
 
+static ssize_t packages_remove_userid_store(struct config_item *item,
+                                      const char *page, size_t count)
+{
+       unsigned int tmp;
+       int ret;
+
+       ret = kstrtouint(page, 10, &tmp);
+       if (ret)
+               return ret;
+       remove_userid_all_entry(tmp);
+       return count;
+}
+
 static struct configfs_attribute packages_attr_packages_gid_list = {
        .ca_name        = "packages_gid.list",
        .ca_mode        = S_IRUGO,
@@ -327,8 +573,11 @@ static struct configfs_attribute packages_attr_packages_gid_list = {
        .show           = packages_list_show,
 };
 
+SDCARDFS_CONFIGFS_ATTR_WO(packages_, remove_userid);
+
 static struct configfs_attribute *packages_attrs[] = {
        &packages_attr_packages_gid_list,
+       &packages_attr_remove_userid,
        NULL,
 };
 
index b03130329014c7bc75b4a04e5f240d8eafa905dc..3434849cee63c9767d7b018f1bbb6ae0684c4331 100644 (file)
@@ -335,6 +335,11 @@ static inline void sdcardfs_put_reset_##pname(const struct dentry *dent) \
 SDCARDFS_DENT_FUNC(lower_path)
 SDCARDFS_DENT_FUNC(orig_path)
 
+static inline bool sbinfo_has_sdcard_magic(struct sdcardfs_sb_info *sbinfo)
+{
+  return sbinfo && sbinfo->sb && sbinfo->sb->s_magic == SDCARDFS_SUPER_MAGIC;
+}
+
 /* grab a refererence if we aren't linking to ourself */
 static inline void set_top(struct sdcardfs_inode_info *info, struct inode *top)
 {
@@ -442,18 +447,28 @@ extern struct list_head sdcardfs_super_list;
 
 /* for packagelist.c */
 extern appid_t get_appid(const char *app_name);
+extern appid_t is_excluded(const char *app_name, userid_t userid);
 extern int check_caller_access_to_name(struct inode *parent_node, const char* name);
 extern int open_flags_to_access_mode(int open_flags);
 extern int packagelist_init(void);
 extern void packagelist_exit(void);
 
 /* for derived_perm.c */
+#define BY_NAME                (1 << 0)
+#define BY_USERID      (1 << 1)
+struct limit_search {
+       unsigned int flags;
+       const char *name;
+       size_t length;
+       userid_t userid;
+};
+
 extern void setup_derived_state(struct inode *inode, perm_t perm, userid_t userid,
                        uid_t uid, bool under_android, struct inode *top);
 extern void get_derived_permission(struct dentry *parent, struct dentry *dentry);
 extern void get_derived_permission_new(struct dentry *parent, struct dentry *dentry, struct dentry *newdentry);
 extern void fixup_top_recursive(struct dentry *parent);
-extern void fixup_perms_recursive(struct dentry *dentry, const char *name, size_t len);
+extern void fixup_perms_recursive(struct dentry *dentry, struct limit_search *limit);
 
 extern void update_derived_permission_lock(struct dentry *dentry);
 extern int need_graft_path(struct dentry *dentry);