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cb26a31157
The way namespace tags are implemented in sysfs is more complicated than necessary. As each tag is a pointer value and required to be non-NULL under a namespace enabled parent, there's no need to record separately what type each tag is or where namespace is enabled. If multiple namespace types are needed, which currently aren't, we can simply compare the tag to a set of allowed tags in the superblock assuming that the tags, being pointers, won't have the same value across multiple types. Also, whether to filter by namespace tag or not can be trivially determined by whether the node has any tagged children or not. This patch rips out kobj_ns_type handling from sysfs. sysfs no longer cares whether specific type of namespace is enabled or not. If a sysfs_dirent has a non-NULL tag, the parent is marked as needing namespace filtering and the value is tested against the allowed set of tags for the superblock (currently only one but increasing this number isn't difficult) and the sysfs_dirent is ignored if it doesn't match. This removes most kobject namespace knowledge from sysfs proper which will enable proper separation and layering of sysfs. The namespace sanity checks in fs/sysfs/dir.c are replaced by the new sanity check in kobject_namespace(). As this is the only place ktype->namespace() is called for sysfs, this doesn't weaken the sanity check significantly. I omitted converting the sanity check in sysfs_do_create_link_sd(). While the check can be shifted to upper layer, mistakes there are well contained and should be easily visible anyway. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
308 lines
7.1 KiB
C
308 lines
7.1 KiB
C
/*
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* fs/sysfs/symlink.c - sysfs symlink implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/mount.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <linux/mutex.h>
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#include <linux/security.h>
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#include "sysfs.h"
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static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,
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struct kobject *target,
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const char *name, int warn)
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{
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struct sysfs_dirent *target_sd = NULL;
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struct sysfs_dirent *sd = NULL;
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struct sysfs_addrm_cxt acxt;
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int error;
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BUG_ON(!name || !parent_sd);
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/* target->sd can go away beneath us but is protected with
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* sysfs_assoc_lock. Fetch target_sd from it.
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*/
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spin_lock(&sysfs_assoc_lock);
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if (target->sd)
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target_sd = sysfs_get(target->sd);
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spin_unlock(&sysfs_assoc_lock);
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error = -ENOENT;
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if (!target_sd)
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goto out_put;
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error = -ENOMEM;
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sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
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if (!sd)
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goto out_put;
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sd->s_ns = target_sd->s_ns;
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sd->s_symlink.target_sd = target_sd;
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target_sd = NULL; /* reference is now owned by the symlink */
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sysfs_addrm_start(&acxt, parent_sd);
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if (warn)
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error = sysfs_add_one(&acxt, sd);
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else
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error = __sysfs_add_one(&acxt, sd);
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sysfs_addrm_finish(&acxt);
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if (error)
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goto out_put;
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return 0;
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out_put:
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sysfs_put(target_sd);
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sysfs_put(sd);
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return error;
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}
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/**
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* sysfs_create_link_sd - create symlink to a given object.
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* @sd: directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link_sd(sd, target, name, 1);
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}
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static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
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const char *name, int warn)
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{
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struct sysfs_dirent *parent_sd = NULL;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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if (!parent_sd)
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return -EFAULT;
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return sysfs_do_create_link_sd(parent_sd, target, name, warn);
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}
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/**
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* sysfs_create_link - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 1);
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}
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EXPORT_SYMBOL_GPL(sysfs_create_link);
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/**
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* sysfs_create_link_nowarn - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*
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* This function does the same as sysfs_create_link(), but it
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* doesn't warn if the link already exists.
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*/
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int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 0);
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}
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/**
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* sysfs_delete_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @name: name of the symlink to remove.
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*
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* Unlike sysfs_remove_link sysfs_delete_link has enough information
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* to successfully delete symlinks in tagged directories.
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*/
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void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
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const char *name)
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{
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const void *ns = NULL;
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spin_lock(&sysfs_assoc_lock);
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if (targ->sd)
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ns = targ->sd->s_ns;
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spin_unlock(&sysfs_assoc_lock);
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sysfs_hash_and_remove(kobj->sd, ns, name);
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}
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/**
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* sysfs_remove_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @name: name of the symlink to remove.
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*/
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void sysfs_remove_link(struct kobject *kobj, const char *name)
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{
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struct sysfs_dirent *parent_sd = NULL;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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sysfs_hash_and_remove(parent_sd, NULL, name);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_link);
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/**
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* sysfs_rename_link_ns - rename symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @old: previous name of the symlink.
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* @new: new name of the symlink.
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* @new_ns: new namespace of the symlink.
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*
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* A helper function for the common rename symlink idiom.
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*/
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int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
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const char *old, const char *new, const void *new_ns)
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{
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struct sysfs_dirent *parent_sd, *sd = NULL;
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const void *old_ns = NULL;
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int result;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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if (targ->sd)
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old_ns = targ->sd->s_ns;
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result = -ENOENT;
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sd = sysfs_get_dirent(parent_sd, old_ns, old);
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if (!sd)
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goto out;
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result = -EINVAL;
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if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
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goto out;
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if (sd->s_symlink.target_sd->s_dir.kobj != targ)
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goto out;
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result = sysfs_rename(sd, parent_sd, new_ns, new);
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out:
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sysfs_put(sd);
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return result;
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}
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EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
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static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
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struct sysfs_dirent *target_sd, char *path)
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{
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struct sysfs_dirent *base, *sd;
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char *s = path;
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int len = 0;
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/* go up to the root, stop at the base */
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base = parent_sd;
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while (base->s_parent) {
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sd = target_sd->s_parent;
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while (sd->s_parent && base != sd)
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sd = sd->s_parent;
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if (base == sd)
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break;
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strcpy(s, "../");
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s += 3;
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base = base->s_parent;
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}
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/* determine end of target string for reverse fillup */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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len += strlen(sd->s_name) + 1;
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sd = sd->s_parent;
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}
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/* check limits */
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if (len < 2)
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return -EINVAL;
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len--;
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if ((s - path) + len > PATH_MAX)
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return -ENAMETOOLONG;
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/* reverse fillup of target string from target to base */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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int slen = strlen(sd->s_name);
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len -= slen;
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strncpy(s + len, sd->s_name, slen);
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if (len)
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s[--len] = '/';
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sd = sd->s_parent;
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}
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return 0;
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}
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static int sysfs_getlink(struct dentry *dentry, char *path)
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{
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struct sysfs_dirent *sd = dentry->d_fsdata;
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struct sysfs_dirent *parent_sd = sd->s_parent;
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struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
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int error;
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mutex_lock(&sysfs_mutex);
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error = sysfs_get_target_path(parent_sd, target_sd, path);
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mutex_unlock(&sysfs_mutex);
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return error;
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}
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static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (page) {
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error = sysfs_getlink(dentry, (char *) page);
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if (error < 0)
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free_page((unsigned long)page);
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}
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nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
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return NULL;
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}
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static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd,
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void *cookie)
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{
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char *page = nd_get_link(nd);
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if (!IS_ERR(page))
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free_page((unsigned long)page);
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}
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const struct inode_operations sysfs_symlink_inode_operations = {
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.setxattr = sysfs_setxattr,
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.readlink = generic_readlink,
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.follow_link = sysfs_follow_link,
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.put_link = sysfs_put_link,
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.setattr = sysfs_setattr,
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.getattr = sysfs_getattr,
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.permission = sysfs_permission,
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};
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