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-rw-r--r--fs/configfs/configfs_internal.h3
-rw-r--r--fs/configfs/dir.c210
-rw-r--r--fs/configfs/symlink.c26
3 files changed, 197 insertions, 42 deletions
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index da015c12e3ea..762d287123ca 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -49,8 +49,10 @@ 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;
extern spinlock_t configfs_dirent_lock;
extern struct vfsmount * configfs_mount;
@@ -66,6 +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 179589be063a..7a8db78a91d2 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)
@@ -283,6 +324,8 @@ static void remove_dir(struct dentry * d)
* The only thing special about this is that we remove any files in
* the directory before we remove the directory, and we've inlined
* what used to be configfs_rmdir() below, instead of calling separately.
+ *
+ * Caller holds the mutex of the item's inode
*/
static void configfs_remove_dir(struct config_item * item)
@@ -330,7 +373,19 @@ 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 +408,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
return simple_lookup(dir, dentry, nd);
}
+out:
return ERR_PTR(err);
}
@@ -370,13 +426,17 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex
struct configfs_dirent *sd;
int ret;
+ /* Mark that we're trying to drop the group */
+ parent_sd->s_type |= CONFIGFS_USET_DROPPING;
+
ret = -EBUSY;
if (!list_empty(&parent_sd->s_links))
goto out;
ret = 0;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
- if (sd->s_type & CONFIGFS_NOT_PINNED)
+ if (!sd->s_element ||
+ (sd->s_type & CONFIGFS_NOT_PINNED))
continue;
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
/* Abort if racing with mkdir() */
@@ -385,8 +445,6 @@ static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex
*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
return -EAGAIN;
}
- /* Mark that we're trying to drop the group */
- sd->s_type |= CONFIGFS_USET_DROPPING;
/*
* Yup, recursive. If there's a problem, blame
@@ -414,12 +472,11 @@ static void configfs_detach_rollback(struct dentry *dentry)
struct configfs_dirent *parent_sd = dentry->d_fsdata;
struct configfs_dirent *sd;
- list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
- if (sd->s_type & CONFIGFS_USET_DEFAULT) {
+ parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
+
+ list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
+ if (sd->s_type & CONFIGFS_USET_DEFAULT)
configfs_detach_rollback(sd->s_dentry);
- sd->s_type &= ~CONFIGFS_USET_DROPPING;
- }
- }
}
static void detach_attrs(struct config_item * item)
@@ -558,36 +615,21 @@ static int create_default_group(struct config_group *parent_group,
static int populate_groups(struct config_group *group)
{
struct config_group *new_group;
- struct dentry *dentry = group->cg_item.ci_dentry;
int ret = 0;
int i;
if (group->default_groups) {
- /*
- * FYI, we're faking mkdir here
- * I'm not sure we need this semaphore, as we're called
- * from our parent's mkdir. That holds our parent's
- * i_mutex, so afaik lookup cannot continue through our
- * parent to find us, let alone mess with our tree.
- * That said, taking our i_mutex is closer to mkdir
- * emulation, and shouldn't hurt.
- */
- mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
-
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
ret = create_default_group(group, new_group);
- if (ret)
+ if (ret) {
+ detach_groups(group);
break;
+ }
}
-
- mutex_unlock(&dentry->d_inode->i_mutex);
}
- if (ret)
- detach_groups(group);
-
return ret;
}
@@ -702,7 +744,15 @@ static int configfs_attach_item(struct config_item *parent_item,
if (!ret) {
ret = populate_attrs(item);
if (ret) {
+ /*
+ * We are going to remove an inode and its dentry but
+ * the VFS may already have hit and used them. Thus,
+ * we must lock them as rmdir() would.
+ */
+ mutex_lock(&dentry->d_inode->i_mutex);
configfs_remove_dir(item);
+ dentry->d_inode->i_flags |= S_DEAD;
+ mutex_unlock(&dentry->d_inode->i_mutex);
d_delete(dentry);
}
}
@@ -710,6 +760,7 @@ static int configfs_attach_item(struct config_item *parent_item,
return ret;
}
+/* Caller holds the mutex of the item's inode */
static void configfs_detach_item(struct config_item *item)
{
detach_attrs(item);
@@ -728,16 +779,30 @@ static int configfs_attach_group(struct config_item *parent_item,
sd = dentry->d_fsdata;
sd->s_type |= CONFIGFS_USET_DIR;
+ /*
+ * FYI, we're faking mkdir in populate_groups()
+ * We must lock the group's inode to avoid races with the VFS
+ * which can already hit the inode and try to add/remove entries
+ * under it.
+ *
+ * We must also lock the inode to remove it safely in case of
+ * error, as rmdir() would.
+ */
+ mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
ret = populate_groups(to_config_group(item));
if (ret) {
configfs_detach_item(item);
- d_delete(dentry);
+ dentry->d_inode->i_flags |= S_DEAD;
}
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ if (ret)
+ d_delete(dentry);
}
return ret;
}
+/* Caller holds the mutex of the group's inode */
static void configfs_detach_group(struct config_item *item)
{
detach_groups(to_config_group(item));
@@ -1035,7 +1100,7 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
struct configfs_subsystem *subsys;
struct configfs_dirent *sd;
struct config_item_type *type;
- struct module *owner = NULL;
+ struct module *subsys_owner = NULL, *new_item_owner = NULL;
char *name;
if (dentry->d_parent == configfs_sb->s_root) {
@@ -1044,6 +1109,16 @@ 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;
@@ -1062,10 +1137,25 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
goto out_put;
}
+ /*
+ * The subsystem may belong to a different module than the item
+ * being created. We don't want to safely pin the new item but
+ * fail to pin the subsystem it sits under.
+ */
+ if (!subsys->su_group.cg_item.ci_type) {
+ ret = -EINVAL;
+ goto out_put;
+ }
+ subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+ if (!try_module_get(subsys_owner)) {
+ ret = -EINVAL;
+ goto out_put;
+ }
+
name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
if (!name) {
ret = -ENOMEM;
- goto out_put;
+ goto out_subsys_put;
}
snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
@@ -1094,10 +1184,10 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
kfree(name);
if (ret) {
/*
- * If item == NULL, then link_obj() was never called.
+ * If ret != 0, then link_obj() was never called.
* There are no extra references to clean up.
*/
- goto out_put;
+ goto out_subsys_put;
}
/*
@@ -1111,8 +1201,8 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
goto out_unlink;
}
- owner = type->ct_owner;
- if (!try_module_get(owner)) {
+ new_item_owner = type->ct_owner;
+ if (!try_module_get(new_item_owner)) {
ret = -EINVAL;
goto out_unlink;
}
@@ -1142,6 +1232,8 @@ 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:
@@ -1159,9 +1251,13 @@ out_unlink:
mutex_unlock(&subsys->su_mutex);
if (module_got)
- module_put(owner);
+ module_put(new_item_owner);
}
+out_subsys_put:
+ if (ret)
+ module_put(subsys_owner);
+
out_put:
/*
* link_obj()/link_group() took a reference from child->parent,
@@ -1180,7 +1276,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
struct config_item *item;
struct configfs_subsystem *subsys;
struct configfs_dirent *sd;
- struct module *owner = NULL;
+ struct module *subsys_owner = NULL, *dead_item_owner = NULL;
int ret;
if (dentry->d_parent == configfs_sb->s_root)
@@ -1207,6 +1303,15 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
return -EINVAL;
}
+ /* configfs_mkdir() shouldn't have allowed this */
+ BUG_ON(!subsys->su_group.cg_item.ci_type);
+ subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
+
+ /*
+ * Ensure that no racing symlink() will make detach_prep() fail while
+ * the new link is temporarily attached
+ */
+ mutex_lock(&configfs_symlink_mutex);
spin_lock(&configfs_dirent_lock);
do {
struct mutex *wait_mutex;
@@ -1215,6 +1320,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
if (ret) {
configfs_detach_rollback(dentry);
spin_unlock(&configfs_dirent_lock);
+ mutex_unlock(&configfs_symlink_mutex);
if (ret != -EAGAIN) {
config_item_put(parent_item);
return ret;
@@ -1224,10 +1330,12 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
mutex_lock(wait_mutex);
mutex_unlock(wait_mutex);
+ mutex_lock(&configfs_symlink_mutex);
spin_lock(&configfs_dirent_lock);
}
} while (ret == -EAGAIN);
spin_unlock(&configfs_dirent_lock);
+ mutex_unlock(&configfs_symlink_mutex);
/* Get a working ref for the duration of this function */
item = configfs_get_config_item(dentry);
@@ -1236,7 +1344,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
config_item_put(parent_item);
if (item->ci_type)
- owner = item->ci_type->ct_owner;
+ dead_item_owner = item->ci_type->ct_owner;
if (sd->s_type & CONFIGFS_USET_DIR) {
configfs_detach_group(item);
@@ -1258,7 +1366,8 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
/* Drop our reference from above */
config_item_put(item);
- module_put(owner);
+ module_put(dead_item_owner);
+ module_put(subsys_owner);
return 0;
}
@@ -1314,13 +1423,24 @@ 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)
@@ -1491,6 +1611,10 @@ 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);
}
}
@@ -1517,11 +1641,13 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
I_MUTEX_PARENT);
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+ mutex_lock(&configfs_symlink_mutex);
spin_lock(&configfs_dirent_lock);
if (configfs_detach_prep(dentry, NULL)) {
printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
}
spin_unlock(&configfs_dirent_lock);
+ mutex_unlock(&configfs_symlink_mutex);
configfs_detach_group(&group->cg_item);
dentry->d_inode->i_flags |= S_DEAD;
mutex_unlock(&dentry->d_inode->i_mutex);
diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c
index 0004d18c40ac..bf74973b0492 100644
--- a/fs/configfs/symlink.c
+++ b/fs/configfs/symlink.c
@@ -31,6 +31,9 @@
#include <linux/configfs.h>
#include "configfs_internal.h"
+/* Protects attachments of new symlinks */
+DEFINE_MUTEX(configfs_symlink_mutex);
+
static int item_depth(struct config_item * item)
{
struct config_item * p = item;
@@ -73,11 +76,20 @@ 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) {
sl->sl_target = config_item_get(item);
spin_lock(&configfs_dirent_lock);
+ if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
+ spin_unlock(&configfs_dirent_lock);
+ config_item_put(item);
+ kfree(sl);
+ return -ENOENT;
+ }
list_add(&sl->sl_list, &target_sd->s_links);
spin_unlock(&configfs_dirent_lock);
ret = configfs_create_link(sl, parent_item->ci_dentry,
@@ -91,6 +103,7 @@ static int create_link(struct config_item *parent_item,
}
}
+out:
return ret;
}
@@ -120,6 +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;
@@ -128,9 +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;
@@ -141,7 +165,9 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna
ret = type->ct_item_ops->allow_link(parent_item, target_item);
if (!ret) {
+ mutex_lock(&configfs_symlink_mutex);
ret = create_link(parent_item, target_item, dentry);
+ mutex_unlock(&configfs_symlink_mutex);
if (ret && type->ct_item_ops->drop_link)
type->ct_item_ops->drop_link(parent_item,
target_item);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.