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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 * Returns the created node on success, ERR_PTR() value on error.
23 * Ownership of the link matches ownership of the target.
24 */
25struct 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|S_IRWXUGO, uid, gid,
40 KERNFS_LINK);
41 if (!kn)
42 return ERR_PTR(-ENOMEM);
43
44 if (kernfs_ns_enabled(parent))
45 kn->ns = target->ns;
46 kn->symlink.target_kn = target;
47 kernfs_get(target); /* ref owned by symlink */
48
49 error = kernfs_add_one(kn);
50 if (!error)
51 return kn;
52
53 kernfs_put(kn);
54 return ERR_PTR(error);
55}
56
57static int kernfs_get_target_path(struct kernfs_node *parent,
58 struct kernfs_node *target, char *path)
59{
60 struct kernfs_node *base, *kn;
61 char *s = path;
62 int len = 0;
63
64 /* go up to the root, stop at the base */
65 base = parent;
66 while (base->parent) {
67 kn = target->parent;
68 while (kn->parent && base != kn)
69 kn = kn->parent;
70
71 if (base == kn)
72 break;
73
74 if ((s - path) + 3 >= PATH_MAX)
75 return -ENAMETOOLONG;
76
77 strcpy(s, "../");
78 s += 3;
79 base = base->parent;
80 }
81
82 /* determine end of target string for reverse fillup */
83 kn = target;
84 while (kn->parent && kn != base) {
85 len += strlen(kn->name) + 1;
86 kn = kn->parent;
87 }
88
89 /* check limits */
90 if (len < 2)
91 return -EINVAL;
92 len--;
93 if ((s - path) + len >= PATH_MAX)
94 return -ENAMETOOLONG;
95
96 /* reverse fillup of target string from target to base */
97 kn = target;
98 while (kn->parent && kn != base) {
99 int slen = strlen(kn->name);
100
101 len -= slen;
102 memcpy(s + len, kn->name, slen);
103 if (len)
104 s[--len] = '/';
105
106 kn = kn->parent;
107 }
108
109 return 0;
110}
111
112static int kernfs_getlink(struct inode *inode, char *path)
113{
114 struct kernfs_node *kn = inode->i_private;
115 struct kernfs_node *parent = kn->parent;
116 struct kernfs_node *target = kn->symlink.target_kn;
117 int error;
118
119 mutex_lock(&kernfs_mutex);
120 error = kernfs_get_target_path(parent, target, path);
121 mutex_unlock(&kernfs_mutex);
122
123 return error;
124}
125
126static const char *kernfs_iop_get_link(struct dentry *dentry,
127 struct inode *inode,
128 struct delayed_call *done)
129{
130 char *body;
131 int error;
132
133 if (!dentry)
134 return ERR_PTR(-ECHILD);
135 body = kzalloc(PAGE_SIZE, GFP_KERNEL);
136 if (!body)
137 return ERR_PTR(-ENOMEM);
138 error = kernfs_getlink(inode, body);
139 if (unlikely(error < 0)) {
140 kfree(body);
141 return ERR_PTR(error);
142 }
143 set_delayed_call(done, kfree_link, body);
144 return body;
145}
146
147const struct inode_operations kernfs_symlink_iops = {
148 .listxattr = kernfs_iop_listxattr,
149 .get_link = kernfs_iop_get_link,
150 .setattr = kernfs_iop_setattr,
151 .getattr = kernfs_iop_getattr,
152 .permission = kernfs_iop_permission,
153};
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 * Returns the created node on success, ERR_PTR() value on error.
23 * Ownership of the link matches ownership of the target.
24 */
25struct 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|S_IRWXUGO, uid, gid,
40 KERNFS_LINK);
41 if (!kn)
42 return ERR_PTR(-ENOMEM);
43
44 if (kernfs_ns_enabled(parent))
45 kn->ns = target->ns;
46 kn->symlink.target_kn = target;
47 kernfs_get(target); /* ref owned by symlink */
48
49 error = kernfs_add_one(kn);
50 if (!error)
51 return kn;
52
53 kernfs_put(kn);
54 return ERR_PTR(error);
55}
56
57static int kernfs_get_target_path(struct kernfs_node *parent,
58 struct kernfs_node *target, char *path)
59{
60 struct kernfs_node *base, *kn;
61 char *s = path;
62 int len = 0;
63
64 /* go up to the root, stop at the base */
65 base = parent;
66 while (base->parent) {
67 kn = target->parent;
68 while (kn->parent && base != kn)
69 kn = kn->parent;
70
71 if (base == kn)
72 break;
73
74 if ((s - path) + 3 >= PATH_MAX)
75 return -ENAMETOOLONG;
76
77 strcpy(s, "../");
78 s += 3;
79 base = base->parent;
80 }
81
82 /* determine end of target string for reverse fillup */
83 kn = target;
84 while (kn->parent && kn != base) {
85 len += strlen(kn->name) + 1;
86 kn = kn->parent;
87 }
88
89 /* check limits */
90 if (len < 2)
91 return -EINVAL;
92 len--;
93 if ((s - path) + len >= PATH_MAX)
94 return -ENAMETOOLONG;
95
96 /* reverse fillup of target string from target to base */
97 kn = target;
98 while (kn->parent && kn != base) {
99 int slen = strlen(kn->name);
100
101 len -= slen;
102 memcpy(s + len, kn->name, slen);
103 if (len)
104 s[--len] = '/';
105
106 kn = kn->parent;
107 }
108
109 return 0;
110}
111
112static int kernfs_getlink(struct inode *inode, char *path)
113{
114 struct kernfs_node *kn = inode->i_private;
115 struct kernfs_node *parent = kn->parent;
116 struct kernfs_node *target = kn->symlink.target_kn;
117 int error;
118
119 mutex_lock(&kernfs_mutex);
120 error = kernfs_get_target_path(parent, target, path);
121 mutex_unlock(&kernfs_mutex);
122
123 return error;
124}
125
126static const char *kernfs_iop_get_link(struct dentry *dentry,
127 struct inode *inode,
128 struct delayed_call *done)
129{
130 char *body;
131 int error;
132
133 if (!dentry)
134 return ERR_PTR(-ECHILD);
135 body = kzalloc(PAGE_SIZE, GFP_KERNEL);
136 if (!body)
137 return ERR_PTR(-ENOMEM);
138 error = kernfs_getlink(inode, body);
139 if (unlikely(error < 0)) {
140 kfree(body);
141 return ERR_PTR(error);
142 }
143 set_delayed_call(done, kfree_link, body);
144 return body;
145}
146
147const struct inode_operations kernfs_symlink_iops = {
148 .listxattr = kernfs_iop_listxattr,
149 .get_link = kernfs_iop_get_link,
150 .setattr = kernfs_iop_setattr,
151 .getattr = kernfs_iop_getattr,
152 .permission = kernfs_iop_permission,
153};