[linux-2.6-block.git] / fs / kernfs / symlink.c

// 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 (kernfs_parent(base)) {
		kn = kernfs_parent(target);
		while (kernfs_parent(kn) && base != kn)
			kn = kernfs_parent(kn);

		if (base == kn)
			break;

		if ((s - path) + 3 >= PATH_MAX)
			return -ENAMETOOLONG;

		strcpy(s, "../");
		s += 3;
		base = kernfs_parent(base);
	}

	/* determine end of target string for reverse fillup */
	kn = target;
	while (kernfs_parent(kn) && kn != base) {
		len += strlen(kernfs_rcu_name(kn)) + 1;
		kn = kernfs_parent(kn);
	}

	/* 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 (kernfs_parent(kn) && kn != base) {
		const char *name = kernfs_rcu_name(kn);
		int slen = strlen(name);

		len -= slen;
		memcpy(s + len, name, slen);
		if (len)
			s[--len] = '/';

		kn = kernfs_parent(kn);
	}

	return 0;
}

static int kernfs_getlink(struct inode *inode, char *path)
{
	struct kernfs_node *kn = inode->i_private;
	struct kernfs_node *parent;
	struct kernfs_node *target = kn->symlink.target_kn;
	struct kernfs_root *root = kernfs_root(kn);
	int error;

	down_read(&root->kernfs_rwsem);
	parent = kernfs_parent(kn);
	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,
};
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0-only
	2	/*
	3	* fs/kernfs/symlink.c - kernfs symlink implementation
	4	*
	5	* Copyright (c) 2001-3 Patrick Mochel
	6	* Copyright (c) 2007 SUSE Linux Products GmbH
	7	* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
	8	*/
	9
	10	#include <linux/fs.h>
	11	#include <linux/gfp.h>
	12	#include <linux/namei.h>
	13
	14	#include "kernfs-internal.h"
	15
	16	/**
	17	* kernfs_create_link - create a symlink
	18	* @parent: directory to create the symlink in
	19	* @name: name of the symlink
	20	* @target: target node for the symlink to point to
	21	*
	22	* Return: the created node on success, ERR_PTR() value on error.
	23	* Ownership of the link matches ownership of the target.
	24	*/
	25	struct kernfs_node kernfs_create_link(struct kernfs_node parent,
	26	const char *name,
	27	struct kernfs_node *target)
	28	{
	29	struct kernfs_node *kn;
	30	int error;
	31	kuid_t uid = GLOBAL_ROOT_UID;
	32	kgid_t gid = GLOBAL_ROOT_GID;
	33
	34	if (target->iattr) {
	35	uid = target->iattr->ia_uid;
	36	gid = target->iattr->ia_gid;
	37	}
	38
	39	kn = kernfs_new_node(parent, name, S_IFLNK\|0777, uid, gid, KERNFS_LINK);
	40	if (!kn)
	41	return ERR_PTR(-ENOMEM);
	42
	43	if (kernfs_ns_enabled(parent))
	44	kn->ns = target->ns;
	45	kn->symlink.target_kn = target;
	46	kernfs_get(target); /* ref owned by symlink */
	47
	48	error = kernfs_add_one(kn);
	49	if (!error)
	50	return kn;
	51
	52	kernfs_put(kn);
	53	return ERR_PTR(error);
	54	}
	55
	56	static int kernfs_get_target_path(struct kernfs_node *parent,
	57	struct kernfs_node target, char path)
	58	{
	59	struct kernfs_node base, kn;
	60	char *s = path;
	61	int len = 0;
	62
	63	/* go up to the root, stop at the base */
	64	base = parent;
	65	while (kernfs_parent(base)) {
	66	kn = kernfs_parent(target);
	67	while (kernfs_parent(kn) && base != kn)
	68	kn = kernfs_parent(kn);
	69
	70	if (base == kn)
	71	break;
	72
	73	if ((s - path) + 3 >= PATH_MAX)
	74	return -ENAMETOOLONG;
	75
	76	strcpy(s, "../");
	77	s += 3;
	78	base = kernfs_parent(base);
	79	}
	80
	81	/* determine end of target string for reverse fillup */
	82	kn = target;
	83	while (kernfs_parent(kn) && kn != base) {
	84	len += strlen(kernfs_rcu_name(kn)) + 1;
	85	kn = kernfs_parent(kn);
	86	}
	87
	88	/* check limits */
	89	if (len < 2)
	90	return -EINVAL;
	91	len--;
	92	if ((s - path) + len >= PATH_MAX)
	93	return -ENAMETOOLONG;
	94
	95	/* reverse fillup of target string from target to base */
	96	kn = target;
	97	while (kernfs_parent(kn) && kn != base) {
	98	const char *name = kernfs_rcu_name(kn);
	99	int slen = strlen(name);
	100
	101	len -= slen;
	102	memcpy(s + len, name, slen);
	103	if (len)
	104	s[--len] = '/';
	105
	106	kn = kernfs_parent(kn);
	107	}
	108
	109	return 0;
	110	}
	111
	112	static int kernfs_getlink(struct inode inode, char path)
	113	{
	114	struct kernfs_node *kn = inode->i_private;
	115	struct kernfs_node *parent;
	116	struct kernfs_node *target = kn->symlink.target_kn;
	117	struct kernfs_root *root = kernfs_root(kn);
	118	int error;
	119
	120	down_read(&root->kernfs_rwsem);
	121	parent = kernfs_parent(kn);
	122	error = kernfs_get_target_path(parent, target, path);
	123	up_read(&root->kernfs_rwsem);
	124
	125	return error;
	126	}
	127
	128	static const char kernfs_iop_get_link(struct dentry dentry,
	129	struct inode *inode,
	130	struct delayed_call *done)
	131	{
	132	char *body;
	133	int error;
	134
	135	if (!dentry)
	136	return ERR_PTR(-ECHILD);
	137	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
	138	if (!body)
	139	return ERR_PTR(-ENOMEM);
	140	error = kernfs_getlink(inode, body);
	141	if (unlikely(error < 0)) {
	142	kfree(body);
	143	return ERR_PTR(error);
	144	}
	145	set_delayed_call(done, kfree_link, body);
	146	return body;
	147	}
	148
	149	const struct inode_operations kernfs_symlink_iops = {
	150	.listxattr = kernfs_iop_listxattr,
	151	.get_link = kernfs_iop_get_link,
	152	.setattr = kernfs_iop_setattr,
	153	.getattr = kernfs_iop_getattr,
	154	.permission = kernfs_iop_permission,
	155	};