[linux.git] / fs / sysfs / symlink.c

// SPDX-License-Identifier: GPL-2.0
/*
 * fs/sysfs/symlink.c - sysfs symlink implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <[email protected]>
 *
 * Please see Documentation/filesystems/sysfs.rst for more information.
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/mutex.h>
#include <linux/security.h>

#include "sysfs.h"

static int sysfs_do_create_link_sd(struct kernfs_node *parent,
                                   struct kobject *target_kobj,
                                   const char *name, int warn)
{
        struct kernfs_node *kn, *target = NULL;

        if (WARN_ON(!name || !parent))
                return -EINVAL;

        /*
         * We don't own @target_kobj and it may be removed at any time.
         * Synchronize using sysfs_symlink_target_lock.  See
         * sysfs_remove_dir() for details.
         */
        spin_lock(&sysfs_symlink_target_lock);
        if (target_kobj->sd) {
                target = target_kobj->sd;
                kernfs_get(target);
        }
        spin_unlock(&sysfs_symlink_target_lock);

        if (!target)
                return -ENOENT;

        kn = kernfs_create_link(parent, name, target);
        kernfs_put(target);

        if (!IS_ERR(kn))
                return 0;

        if (warn && PTR_ERR(kn) == -EEXIST)
                sysfs_warn_dup(parent, name);
        return PTR_ERR(kn);
}

/**
 *      sysfs_create_link_sd - create symlink to a given object.
 *      @kn:            directory we're creating the link in.
 *      @target:        object we're pointing to.
 *      @name:          name of the symlink.
 */
int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
                         const char *name)
{
        return sysfs_do_create_link_sd(kn, target, name, 1);
}

static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
                                const char *name, int warn)
{
        struct kernfs_node *parent = NULL;

        if (!kobj)
                parent = sysfs_root_kn;
        else
                parent = kobj->sd;

        if (!parent)
                return -EFAULT;

        return sysfs_do_create_link_sd(parent, target, name, warn);
}

/**
 *      sysfs_create_link - create symlink between two objects.
 *      @kobj:  object whose directory we're creating the link in.
 *      @target:        object we're pointing to.
 *      @name:          name of the symlink.
 */
int sysfs_create_link(struct kobject *kobj, struct kobject *target,
                      const char *name)
{
        return sysfs_do_create_link(kobj, target, name, 1);
}
EXPORT_SYMBOL_GPL(sysfs_create_link);

/**
 *      sysfs_create_link_nowarn - create symlink between two objects.
 *      @kobj:  object whose directory we're creating the link in.
 *      @target:        object we're pointing to.
 *      @name:          name of the symlink.
 *
 *      This function does the same as sysfs_create_link(), but it
 *      doesn't warn if the link already exists.
 */
int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
                             const char *name)
{
        return sysfs_do_create_link(kobj, target, name, 0);
}
EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);

/**
 *      sysfs_delete_link - remove symlink in object's directory.
 *      @kobj:  object we're acting for.
 *      @targ:  object we're pointing to.
 *      @name:  name of the symlink to remove.
 *
 *      Unlike sysfs_remove_link sysfs_delete_link has enough information
 *      to successfully delete symlinks in tagged directories.
 */
void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
                        const char *name)
{
        const void *ns = NULL;

        /*
         * We don't own @target and it may be removed at any time.
         * Synchronize using sysfs_symlink_target_lock.  See
         * sysfs_remove_dir() for details.
         */
        spin_lock(&sysfs_symlink_target_lock);
        if (targ->sd && kernfs_ns_enabled(kobj->sd))
                ns = targ->sd->ns;
        spin_unlock(&sysfs_symlink_target_lock);
        kernfs_remove_by_name_ns(kobj->sd, name, ns);
}

/**
 *      sysfs_remove_link - remove symlink in object's directory.
 *      @kobj:  object we're acting for.
 *      @name:  name of the symlink to remove.
 */
void sysfs_remove_link(struct kobject *kobj, const char *name)
{
        struct kernfs_node *parent = NULL;

        if (!kobj)
                parent = sysfs_root_kn;
        else
                parent = kobj->sd;

        kernfs_remove_by_name(parent, name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_link);

/**
 *      sysfs_rename_link_ns - rename symlink in object's directory.
 *      @kobj:  object we're acting for.
 *      @targ:  object we're pointing to.
 *      @old:   previous name of the symlink.
 *      @new:   new name of the symlink.
 *      @new_ns: new namespace of the symlink.
 *
 *      A helper function for the common rename symlink idiom.
 */
int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
                         const char *old, const char *new, const void *new_ns)
{
        struct kernfs_node *parent, *kn = NULL;
        const void *old_ns = NULL;
        int result;

        if (!kobj)
                parent = sysfs_root_kn;
        else
                parent = kobj->sd;

        if (targ->sd)
                old_ns = targ->sd->ns;

        result = -ENOENT;
        kn = kernfs_find_and_get_ns(parent, old, old_ns);
        if (!kn)
                goto out;

        result = -EINVAL;
        if (kernfs_type(kn) != KERNFS_LINK)
                goto out;
        if (kn->symlink.target_kn->priv != targ)
                goto out;

        result = kernfs_rename_ns(kn, parent, new, new_ns);

out:
        kernfs_put(kn);
        return result;
}
EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);