Contributors: 15
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Joel Becker |
799 |
72.64% |
2 |
6.90% |
| Al Viro |
139 |
12.64% |
6 |
20.69% |
| Louis Rilling |
134 |
12.18% |
5 |
17.24% |
| Christian Brauner |
8 |
0.73% |
4 |
13.79% |
| Jan Blunck |
6 |
0.55% |
2 |
6.90% |
| Bhumika Goyal |
2 |
0.18% |
1 |
3.45% |
| Linus Torvalds (pre-git) |
2 |
0.18% |
1 |
3.45% |
| Harvey Harrison |
2 |
0.18% |
1 |
3.45% |
| Subrata Modak |
2 |
0.18% |
1 |
3.45% |
| Arjan van de Ven |
1 |
0.09% |
1 |
3.45% |
| Linus Torvalds |
1 |
0.09% |
1 |
3.45% |
| Thomas Gleixner |
1 |
0.09% |
1 |
3.45% |
| Honggang Li |
1 |
0.09% |
1 |
3.45% |
| Masahiro Yamada |
1 |
0.09% |
1 |
3.45% |
| Guenter Roeck |
1 |
0.09% |
1 |
3.45% |
| Total |
1100 |
|
29 |
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* symlink.c - operations for configfs symlinks.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/slab.h>
#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;
int depth = 0;
do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
return depth;
}
static int item_path_length(struct config_item * item)
{
struct config_item * p = item;
int length = 1;
do {
length += strlen(config_item_name(p)) + 1;
p = p->ci_parent;
} while (p && !configfs_is_root(p));
return length;
}
static void fill_item_path(struct config_item * item, char * buffer, int length)
{
struct config_item * p;
--length;
for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
int cur = strlen(config_item_name(p));
/* back up enough to print this bus id with '/' */
length -= cur;
memcpy(buffer + length, config_item_name(p), cur);
*(buffer + --length) = '/';
}
}
static int configfs_get_target_path(struct config_item *item,
struct config_item *target, char *path)
{
int depth, size;
char *s;
depth = item_depth(item);
size = item_path_length(target) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_item_path(target, path, size);
pr_debug("%s: path = '%s'\n", __func__, path);
return 0;
}
static int create_link(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
{
struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
char *body;
int ret;
if (!configfs_dirent_is_ready(target_sd))
return -ENOENT;
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return -ENOMEM;
configfs_get(target_sd);
spin_lock(&configfs_dirent_lock);
if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
spin_unlock(&configfs_dirent_lock);
configfs_put(target_sd);
kfree(body);
return -ENOENT;
}
target_sd->s_links++;
spin_unlock(&configfs_dirent_lock);
ret = configfs_get_target_path(parent_item, item, body);
if (!ret)
ret = configfs_create_link(target_sd, parent_item->ci_dentry,
dentry, body);
if (ret) {
spin_lock(&configfs_dirent_lock);
target_sd->s_links--;
spin_unlock(&configfs_dirent_lock);
configfs_put(target_sd);
kfree(body);
}
return ret;
}
static int get_target(const char *symname, struct path *path,
struct config_item **target, struct super_block *sb)
{
int ret;
ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, path);
if (!ret) {
if (path->dentry->d_sb == sb) {
*target = configfs_get_config_item(path->dentry);
if (!*target) {
ret = -ENOENT;
path_put(path);
}
} else {
ret = -EPERM;
path_put(path);
}
}
return ret;
}
int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, const char *symname)
{
int ret;
struct path path;
struct configfs_dirent *sd;
struct config_item *parent_item;
struct config_item *target_item = NULL;
const struct config_item_type *type;
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))
return -ENOENT;
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;
/*
* This is really sick. What they wanted was a hybrid of
* link(2) and symlink(2) - they wanted the target resolved
* at syscall time (as link(2) would've done), be a directory
* (which link(2) would've refused to do) *AND* be a deep
* fucking magic, making the target busy from rmdir POV.
* symlink(2) is nothing of that sort, and the locking it
* gets matches the normal symlink(2) semantics. Without
* attempts to resolve the target (which might very well
* not even exist yet) done prior to locking the parent
* directory. This perversion, OTOH, needs to resolve
* the target, which would lead to obvious deadlocks if
* attempted with any directories locked.
*
* Unfortunately, that garbage is userland ABI and we should've
* said "no" back in 2005. Too late now, so we get to
* play very ugly games with locking.
*
* Try *ANYTHING* of that sort in new code, and you will
* really regret it. Just ask yourself - what could a BOFH
* do to me and do I want to find it out first-hand?
*
* AV, a thoroughly annoyed bastard.
*/
inode_unlock(dir);
ret = get_target(symname, &path, &target_item, dentry->d_sb);
inode_lock(dir);
if (ret)
goto out_put;
if (dentry->d_inode || d_unhashed(dentry))
ret = -EEXIST;
else
ret = inode_permission(&nop_mnt_idmap, dir,
MAY_WRITE | MAY_EXEC);
if (!ret)
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);
}
config_item_put(target_item);
path_put(&path);
out_put:
config_item_put(parent_item);
return ret;
}
int configfs_unlink(struct inode *dir, struct dentry *dentry)
{
struct configfs_dirent *sd = dentry->d_fsdata, *target_sd;
struct config_item *parent_item;
const struct config_item_type *type;
int ret;
ret = -EPERM; /* What lack-of-symlink returns */
if (!(sd->s_type & CONFIGFS_ITEM_LINK))
goto out;
target_sd = sd->s_element;
parent_item = configfs_get_config_item(dentry->d_parent);
type = parent_item->ci_type;
spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
spin_unlock(&configfs_dirent_lock);
configfs_drop_dentry(sd, dentry->d_parent);
dput(dentry);
configfs_put(sd);
/*
* drop_link() must be called before
* decrementing target's ->s_links, so that the order of
* drop_link(this, target) and drop_item(target) is preserved.
*/
if (type && type->ct_item_ops &&
type->ct_item_ops->drop_link)
type->ct_item_ops->drop_link(parent_item,
target_sd->s_element);
spin_lock(&configfs_dirent_lock);
target_sd->s_links--;
spin_unlock(&configfs_dirent_lock);
configfs_put(target_sd);
config_item_put(parent_item);
ret = 0;
out:
return ret;
}
const struct inode_operations configfs_symlink_inode_operations = {
.get_link = simple_get_link,
.setattr = configfs_setattr,
};