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authorLouis Rilling <louis.rilling@kerlabs.com>2008-07-04 18:56:05 +0400
committerMark Fasheh <mfasheh@suse.com>2008-08-01 03:21:13 +0400
commit2a109f2a4155f168047aa2f5b3a170e279bef89a (patch)
tree8e9a080046fb1abdba10e288b89e92cc4c39f6ea
parent9a73d78cda750f12e25eb811878f2d9dbab1bc6e (diff)
downloadlinux-2a109f2a4155f168047aa2f5b3a170e279bef89a.tar.xz
[PATCH] configfs: Prevent userspace from creating new entries under attaching directories
process 1: process 2: configfs_mkdir("A") attach_group("A") attach_item("A") d_instantiate("A") populate_groups("A") mutex_lock("A") attach_group("A/B") attach_item("A") d_instantiate("A/B") mkdir("A/B/C") do_path_lookup("A/B/C", LOOKUP_PARENT) ok lookup_create("A/B/C") mutex_lock("A/B") ok configfs_mkdir("A/B/C") ok attach_group("A/C") attach_item("A/C") d_instantiate("A/C") populate_groups("A/C") mutex_lock("A/C") attach_group("A/C/D") attach_item("A/C/D") failure mutex_unlock("A/C") detach_groups("A/C") nothing to do mkdir("A/C/E") do_path_lookup("A/C/E", LOOKUP_PARENT) ok lookup_create("A/C/E") mutex_lock("A/C") ok configfs_mkdir("A/C/E") ok detach_item("A/C") d_delete("A/C") mutex_unlock("A") detach_groups("A") mutex_lock("A/B") detach_group("A/B") detach_groups("A/B") nothing since no _default_ group detach_item("A/B") mutex_unlock("A/B") d_delete("A/B") detach_item("A") d_delete("A") Two bugs: 1/ "A/B/C" and "A/C/E" are created, but never removed while their parent are removed in the end. The same could happen with symlink() instead of mkdir(). 2/ "A" and "A/C" inodes are not locked while detach_item() is called on them, which may probably confuse VFS. This commit fixes 1/, tagging new directories with CONFIGFS_USET_CREATING before building the inode and instantiating the dentry, and validating the whole group+default groups hierarchy in a second pass by clearing CONFIGFS_USET_CREATING. mkdir(), symlink(), lookup(), and dir_open() simply return -ENOENT if called in (or linking to) a directory tagged with CONFIGFS_USET_CREATING. This does not prevent userspace from calling stat() successfuly on such directories, but this prevents userspace from adding (children to | symlinking from/to | read/write attributes of | listing the contents of) not validated items. In other words, userspace will not interact with the subsystem on a new item until the new item creation completes correctly. It was first proposed to re-use CONFIGFS_USET_IN_MKDIR instead of a new flag CONFIGFS_USET_CREATING, but this generated conflicts when checking the target of a new symlink: a valid target directory in the middle of attaching a new user-created child item could be wrongly detected as being attached. 2/ is fixed by next commit. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
-rw-r--r--fs/configfs/configfs_internal.h2
-rw-r--r--fs/configfs/dir.c91
-rw-r--r--fs/configfs/symlink.c15
3 files changed, 103 insertions, 5 deletions
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index 5f61b26eba9e..762d287123ca 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -49,6 +49,7 @@ struct configfs_dirent {
#define CONFIGFS_USET_DEFAULT 0x0080
#define CONFIGFS_USET_DROPPING 0x0100
#define CONFIGFS_USET_IN_MKDIR 0x0200
+#define CONFIGFS_USET_CREATING 0x0400
#define CONFIGFS_NOT_PINNED (CONFIGFS_ITEM_ATTR)
extern struct mutex configfs_symlink_mutex;
@@ -67,6 +68,7 @@ extern void configfs_inode_exit(void);
extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
extern int configfs_make_dirent(struct configfs_dirent *,
struct dentry *, void *, umode_t, int);
+extern int configfs_dirent_is_ready(struct configfs_dirent *);
extern int configfs_add_file(struct dentry *, const struct configfs_attribute *, int);
extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 4e228c80fe9f..647499a3479b 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -185,7 +185,7 @@ static int create_dir(struct config_item * k, struct dentry * p,
error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
if (!error)
error = configfs_make_dirent(p->d_fsdata, d, k, mode,
- CONFIGFS_DIR);
+ CONFIGFS_DIR | CONFIGFS_USET_CREATING);
if (!error) {
error = configfs_create(d, mode, init_dir);
if (!error) {
@@ -209,6 +209,9 @@ static int create_dir(struct config_item * k, struct dentry * p,
* configfs_create_dir - create a directory for an config_item.
* @item: config_itemwe're creating directory for.
* @dentry: config_item's dentry.
+ *
+ * Note: user-created entries won't be allowed under this new directory
+ * until it is validated by configfs_dir_set_ready()
*/
static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
@@ -231,6 +234,44 @@ static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
return error;
}
+/*
+ * Allow userspace to create new entries under a new directory created with
+ * configfs_create_dir(), and under all of its chidlren directories recursively.
+ * @sd configfs_dirent of the new directory to validate
+ *
+ * Caller must hold configfs_dirent_lock.
+ */
+static void configfs_dir_set_ready(struct configfs_dirent *sd)
+{
+ struct configfs_dirent *child_sd;
+
+ sd->s_type &= ~CONFIGFS_USET_CREATING;
+ list_for_each_entry(child_sd, &sd->s_children, s_sibling)
+ if (child_sd->s_type & CONFIGFS_USET_CREATING)
+ configfs_dir_set_ready(child_sd);
+}
+
+/*
+ * Check that a directory does not belong to a directory hierarchy being
+ * attached and not validated yet.
+ * @sd configfs_dirent of the directory to check
+ *
+ * @return non-zero iff the directory was validated
+ *
+ * Note: takes configfs_dirent_lock, so the result may change from false to true
+ * in two consecutive calls, but never from true to false.
+ */
+int configfs_dirent_is_ready(struct configfs_dirent *sd)
+{
+ int ret;
+
+ spin_lock(&configfs_dirent_lock);
+ ret = !(sd->s_type & CONFIGFS_USET_CREATING);
+ spin_unlock(&configfs_dirent_lock);
+
+ return ret;
+}
+
int configfs_create_link(struct configfs_symlink *sl,
struct dentry *parent,
struct dentry *dentry)
@@ -330,7 +371,19 @@ static struct dentry * configfs_lookup(struct inode *dir,
struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
struct configfs_dirent * sd;
int found = 0;
- int err = 0;
+ int err;
+
+ /*
+ * Fake invisibility if dir belongs to a group/default groups hierarchy
+ * being attached
+ *
+ * This forbids userspace to read/write attributes of items which may
+ * not complete their initialization, since the dentries of the
+ * attributes won't be instantiated.
+ */
+ err = -ENOENT;
+ if (!configfs_dirent_is_ready(parent_sd))
+ goto out;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_NOT_PINNED) {
@@ -353,6 +406,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
return simple_lookup(dir, dentry, nd);
}
+out:
return ERR_PTR(err);
}
@@ -1044,6 +1098,16 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
}
sd = dentry->d_parent->d_fsdata;
+
+ /*
+ * Fake invisibility if dir belongs to a group/default groups hierarchy
+ * being attached
+ */
+ if (!configfs_dirent_is_ready(sd)) {
+ ret = -ENOENT;
+ goto out;
+ }
+
if (!(sd->s_type & CONFIGFS_USET_DIR)) {
ret = -EPERM;
goto out;
@@ -1142,6 +1206,8 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
spin_lock(&configfs_dirent_lock);
sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
+ if (!ret)
+ configfs_dir_set_ready(dentry->d_fsdata);
spin_unlock(&configfs_dirent_lock);
out_unlink:
@@ -1322,13 +1388,24 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
{
struct dentry * dentry = file->f_path.dentry;
struct configfs_dirent * parent_sd = dentry->d_fsdata;
+ int err;
mutex_lock(&dentry->d_inode->i_mutex);
- file->private_data = configfs_new_dirent(parent_sd, NULL);
+ /*
+ * Fake invisibility if dir belongs to a group/default groups hierarchy
+ * being attached
+ */
+ err = -ENOENT;
+ if (configfs_dirent_is_ready(parent_sd)) {
+ file->private_data = configfs_new_dirent(parent_sd, NULL);
+ if (IS_ERR(file->private_data))
+ err = PTR_ERR(file->private_data);
+ else
+ err = 0;
+ }
mutex_unlock(&dentry->d_inode->i_mutex);
- return IS_ERR(file->private_data) ? PTR_ERR(file->private_data) : 0;
-
+ return err;
}
static int configfs_dir_close(struct inode *inode, struct file *file)
@@ -1499,6 +1576,10 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
if (err) {
d_delete(dentry);
dput(dentry);
+ } else {
+ spin_lock(&configfs_dirent_lock);
+ configfs_dir_set_ready(dentry->d_fsdata);
+ spin_unlock(&configfs_dirent_lock);
}
}
diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index 61a886dbd601..bf74973b0492 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -76,6 +76,9 @@ static int create_link(struct config_item *parent_item,
struct configfs_symlink *sl;
int ret;
+ ret = -ENOENT;
+ if (!configfs_dirent_is_ready(target_sd))
+ goto out;
ret = -ENOMEM;
sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL);
if (sl) {
@@ -100,6 +103,7 @@ static int create_link(struct config_item *parent_item,
}
}
+out:
return ret;
}
@@ -129,6 +133,7 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
{
int ret;
struct nameidata nd;
+ struct configfs_dirent *sd;
struct config_item *parent_item;
struct config_item *target_item;
struct config_item_type *type;
@@ -137,9 +142,19 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
if (dentry->d_parent == configfs_sb->s_root)
goto out;
+ sd = dentry->d_parent->d_fsdata;
+ /*
+ * Fake invisibility if dir belongs to a group/default groups hierarchy
+ * being attached
+ */
+ ret = -ENOENT;
+ if (!configfs_dirent_is_ready(sd))
+ goto out;
+
parent_item = configfs_get_config_item(dentry->d_parent);
type = parent_item->ci_type;
+ ret = -EPERM;
if (!type || !type->ct_item_ops ||
!type->ct_item_ops->allow_link)
goto out_put;