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// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/kernfs/symlink.c - kernfs symlink implementation
*
* Copyright (c) 2001-3 Patrick Mochel
* Copyright (c) 2007 SUSE Linux Products GmbH
* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
*/
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/namei.h>
#include "kernfs-internal.h"
/**
* kernfs_create_link - create a symlink
* @parent: directory to create the symlink in
* @name: name of the symlink
* @target: target node for the symlink to point to
*
* Return: the created node on success, ERR_PTR() value on error.
* Ownership of the link matches ownership of the target.
*/
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target)
{
struct kernfs_node *kn;
int error;
kuid_t uid = GLOBAL_ROOT_UID;
kgid_t gid = GLOBAL_ROOT_GID;
if (target->iattr) {
uid = target->iattr->ia_uid;
gid = target->iattr->ia_gid;
}
kn = kernfs_new_node(parent, name, S_IFLNK|0777, uid, gid, KERNFS_LINK);
if (!kn)
return ERR_PTR(-ENOMEM);
if (kernfs_ns_enabled(parent))
kn->ns = target->ns;
kn->symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */
error = kernfs_add_one(kn);
if (!error)
return kn;
kernfs_put(kn);
return ERR_PTR(error);
}
static int kernfs_get_target_path(struct kernfs_node *parent,
struct kernfs_node *target, char *path)
{
struct kernfs_node *base, *kn;
char *s = path;
int len = 0;
/* go up to the root, stop at the base */
base = parent;
while (base->parent) {
kn = target->parent;
while (kn->parent && base != kn)
kn = kn->parent;
if (base == kn)
break;
if ((s - path) + 3 >= PATH_MAX)
return -ENAMETOOLONG;
strcpy(s, "../");
s += 3;
base = base->parent;
}
/* determine end of target string for reverse fillup */
kn = target;
while (kn->parent && kn != base) {
len += strlen(kn->name) + 1;
kn = kn->parent;
}
/* check limits */
if (len < 2)
return -EINVAL;
len--;
if ((s - path) + len >= PATH_MAX)
return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */
kn = target;
while (kn->parent && kn != base) {
int slen = strlen(kn->name);
len -= slen;
memcpy(s + len, kn->name, slen);
if (len)
s[--len] = '/';
kn = kn->parent;
}
return 0;
}
static int kernfs_getlink(struct inode *inode, char *path)
{
struct kernfs_node *kn = inode->i_private;
struct kernfs_node *parent = kn->parent;
struct kernfs_node *target = kn->symlink.target_kn;
struct kernfs_root *root = kernfs_root(parent);
int error;
down_read(&root->kernfs_rwsem);
error = kernfs_get_target_path(parent, target, path);
up_read(&root->kernfs_rwsem);
return error;
}
static const char *kernfs_iop_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
char *body;
int error;
if (!dentry)
return ERR_PTR(-ECHILD);
body = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (!body)
return ERR_PTR(-ENOMEM);
error = kernfs_getlink(inode, body);
if (unlikely(error < 0)) {
kfree(body);
return ERR_PTR(error);
}
set_delayed_call(done, kfree_link, body);
return body;
}
const struct inode_operations kernfs_symlink_iops = {
.listxattr = kernfs_iop_listxattr,
.get_link = kernfs_iop_get_link,
.setattr = kernfs_iop_setattr,
.getattr = kernfs_iop_getattr,
.permission = kernfs_iop_permission,
};
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