2a109f2a41
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>
157 lines
4.9 KiB
C
157 lines
4.9 KiB
C
/* -*- mode: c; c-basic-offset:8; -*-
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* vim: noexpandtab sw=8 ts=8 sts=0:
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*
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* configfs_internal.h - Internal stuff for configfs
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*
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* Based on sysfs:
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* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
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*
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* configfs Copyright (C) 2005 Oracle. All rights reserved.
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*/
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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struct configfs_dirent {
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atomic_t s_count;
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int s_dependent_count;
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struct list_head s_sibling;
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struct list_head s_children;
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struct list_head s_links;
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void * s_element;
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int s_type;
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umode_t s_mode;
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struct dentry * s_dentry;
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struct iattr * s_iattr;
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};
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#define CONFIGFS_ROOT 0x0001
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#define CONFIGFS_DIR 0x0002
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#define CONFIGFS_ITEM_ATTR 0x0004
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#define CONFIGFS_ITEM_LINK 0x0020
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#define CONFIGFS_USET_DIR 0x0040
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#define CONFIGFS_USET_DEFAULT 0x0080
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#define CONFIGFS_USET_DROPPING 0x0100
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#define CONFIGFS_USET_IN_MKDIR 0x0200
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#define CONFIGFS_USET_CREATING 0x0400
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#define CONFIGFS_NOT_PINNED (CONFIGFS_ITEM_ATTR)
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extern struct mutex configfs_symlink_mutex;
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extern spinlock_t configfs_dirent_lock;
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extern struct vfsmount * configfs_mount;
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extern struct kmem_cache *configfs_dir_cachep;
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extern int configfs_is_root(struct config_item *item);
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extern struct inode * configfs_new_inode(mode_t mode, struct configfs_dirent *);
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extern int configfs_create(struct dentry *, int mode, int (*init)(struct inode *));
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extern int configfs_inode_init(void);
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extern void configfs_inode_exit(void);
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extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
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extern int configfs_make_dirent(struct configfs_dirent *,
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struct dentry *, void *, umode_t, int);
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extern int configfs_dirent_is_ready(struct configfs_dirent *);
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extern int configfs_add_file(struct dentry *, const struct configfs_attribute *, int);
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extern void configfs_hash_and_remove(struct dentry * dir, const char * name);
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extern const unsigned char * configfs_get_name(struct configfs_dirent *sd);
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extern void configfs_drop_dentry(struct configfs_dirent *sd, struct dentry *parent);
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extern int configfs_setattr(struct dentry *dentry, struct iattr *iattr);
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extern int configfs_pin_fs(void);
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extern void configfs_release_fs(void);
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extern struct rw_semaphore configfs_rename_sem;
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extern struct super_block * configfs_sb;
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extern const struct file_operations configfs_dir_operations;
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extern const struct file_operations configfs_file_operations;
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extern const struct file_operations bin_fops;
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extern const struct inode_operations configfs_dir_inode_operations;
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extern const struct inode_operations configfs_symlink_inode_operations;
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extern int configfs_symlink(struct inode *dir, struct dentry *dentry,
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const char *symname);
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extern int configfs_unlink(struct inode *dir, struct dentry *dentry);
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struct configfs_symlink {
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struct list_head sl_list;
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struct config_item *sl_target;
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};
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extern int configfs_create_link(struct configfs_symlink *sl,
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struct dentry *parent,
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struct dentry *dentry);
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static inline struct config_item * to_item(struct dentry * dentry)
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{
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struct configfs_dirent * sd = dentry->d_fsdata;
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return ((struct config_item *) sd->s_element);
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}
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static inline struct configfs_attribute * to_attr(struct dentry * dentry)
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{
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struct configfs_dirent * sd = dentry->d_fsdata;
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return ((struct configfs_attribute *) sd->s_element);
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}
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static inline struct config_item *configfs_get_config_item(struct dentry *dentry)
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{
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struct config_item * item = NULL;
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spin_lock(&dcache_lock);
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if (!d_unhashed(dentry)) {
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struct configfs_dirent * sd = dentry->d_fsdata;
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if (sd->s_type & CONFIGFS_ITEM_LINK) {
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struct configfs_symlink * sl = sd->s_element;
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item = config_item_get(sl->sl_target);
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} else
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item = config_item_get(sd->s_element);
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}
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spin_unlock(&dcache_lock);
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return item;
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}
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static inline void release_configfs_dirent(struct configfs_dirent * sd)
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{
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if (!(sd->s_type & CONFIGFS_ROOT)) {
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kfree(sd->s_iattr);
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kmem_cache_free(configfs_dir_cachep, sd);
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}
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}
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static inline struct configfs_dirent * configfs_get(struct configfs_dirent * sd)
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{
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if (sd) {
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WARN_ON(!atomic_read(&sd->s_count));
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atomic_inc(&sd->s_count);
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}
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return sd;
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}
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static inline void configfs_put(struct configfs_dirent * sd)
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{
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WARN_ON(!atomic_read(&sd->s_count));
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if (atomic_dec_and_test(&sd->s_count))
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release_configfs_dirent(sd);
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}
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