Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 : /*
3 : * fs/anon_inodes.c
4 : *
5 : * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
6 : *
7 : * Thanks to Arnd Bergmann for code review and suggestions.
8 : * More changes for Thomas Gleixner suggestions.
9 : *
10 : */
11 :
12 : #include <linux/cred.h>
13 : #include <linux/file.h>
14 : #include <linux/poll.h>
15 : #include <linux/sched.h>
16 : #include <linux/init.h>
17 : #include <linux/fs.h>
18 : #include <linux/mount.h>
19 : #include <linux/module.h>
20 : #include <linux/kernel.h>
21 : #include <linux/magic.h>
22 : #include <linux/anon_inodes.h>
23 : #include <linux/pseudo_fs.h>
24 :
25 : #include <linux/uaccess.h>
26 :
27 : static struct vfsmount *anon_inode_mnt __read_mostly;
28 : static struct inode *anon_inode_inode;
29 :
30 : /*
31 : * anon_inodefs_dname() is called from d_path().
32 : */
33 0 : static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
34 : {
35 0 : return dynamic_dname(buffer, buflen, "anon_inode:%s",
36 : dentry->d_name.name);
37 : }
38 :
39 : static const struct dentry_operations anon_inodefs_dentry_operations = {
40 : .d_dname = anon_inodefs_dname,
41 : };
42 :
43 1 : static int anon_inodefs_init_fs_context(struct fs_context *fc)
44 : {
45 1 : struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC);
46 1 : if (!ctx)
47 : return -ENOMEM;
48 1 : ctx->dops = &anon_inodefs_dentry_operations;
49 1 : return 0;
50 : }
51 :
52 : static struct file_system_type anon_inode_fs_type = {
53 : .name = "anon_inodefs",
54 : .init_fs_context = anon_inodefs_init_fs_context,
55 : .kill_sb = kill_anon_super,
56 : };
57 :
58 0 : static struct inode *anon_inode_make_secure_inode(
59 : const char *name,
60 : const struct inode *context_inode)
61 : {
62 : struct inode *inode;
63 0 : const struct qstr qname = QSTR_INIT(name, strlen(name));
64 : int error;
65 :
66 0 : inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
67 0 : if (IS_ERR(inode))
68 : return inode;
69 0 : inode->i_flags &= ~S_PRIVATE;
70 0 : error = security_inode_init_security_anon(inode, &qname, context_inode);
71 : if (error) {
72 : iput(inode);
73 : return ERR_PTR(error);
74 : }
75 : return inode;
76 : }
77 :
78 0 : static struct file *__anon_inode_getfile(const char *name,
79 : const struct file_operations *fops,
80 : void *priv, int flags,
81 : const struct inode *context_inode,
82 : bool secure)
83 : {
84 : struct inode *inode;
85 : struct file *file;
86 :
87 : if (fops->owner && !try_module_get(fops->owner))
88 : return ERR_PTR(-ENOENT);
89 :
90 0 : if (secure) {
91 0 : inode = anon_inode_make_secure_inode(name, context_inode);
92 0 : if (IS_ERR(inode)) {
93 : file = ERR_CAST(inode);
94 : goto err;
95 : }
96 : } else {
97 0 : inode = anon_inode_inode;
98 0 : if (IS_ERR(inode)) {
99 : file = ERR_PTR(-ENODEV);
100 : goto err;
101 : }
102 : /*
103 : * We know the anon_inode inode count is always
104 : * greater than zero, so ihold() is safe.
105 : */
106 0 : ihold(inode);
107 : }
108 :
109 0 : file = alloc_file_pseudo(inode, anon_inode_mnt, name,
110 : flags & (O_ACCMODE | O_NONBLOCK), fops);
111 0 : if (IS_ERR(file))
112 : goto err_iput;
113 :
114 0 : file->f_mapping = inode->i_mapping;
115 :
116 0 : file->private_data = priv;
117 :
118 0 : return file;
119 :
120 : err_iput:
121 0 : iput(inode);
122 : err:
123 0 : module_put(fops->owner);
124 0 : return file;
125 : }
126 :
127 : /**
128 : * anon_inode_getfile - creates a new file instance by hooking it up to an
129 : * anonymous inode, and a dentry that describe the "class"
130 : * of the file
131 : *
132 : * @name: [in] name of the "class" of the new file
133 : * @fops: [in] file operations for the new file
134 : * @priv: [in] private data for the new file (will be file's private_data)
135 : * @flags: [in] flags
136 : *
137 : * Creates a new file by hooking it on a single inode. This is useful for files
138 : * that do not need to have a full-fledged inode in order to operate correctly.
139 : * All the files created with anon_inode_getfile() will share a single inode,
140 : * hence saving memory and avoiding code duplication for the file/inode/dentry
141 : * setup. Returns the newly created file* or an error pointer.
142 : */
143 0 : struct file *anon_inode_getfile(const char *name,
144 : const struct file_operations *fops,
145 : void *priv, int flags)
146 : {
147 0 : return __anon_inode_getfile(name, fops, priv, flags, NULL, false);
148 : }
149 : EXPORT_SYMBOL_GPL(anon_inode_getfile);
150 :
151 : /**
152 : * anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new
153 : * !S_PRIVATE anon inode rather than reuse the
154 : * singleton anon inode and calls the
155 : * inode_init_security_anon() LSM hook. This
156 : * allows for both the inode to have its own
157 : * security context and for the LSM to enforce
158 : * policy on the inode's creation.
159 : *
160 : * @name: [in] name of the "class" of the new file
161 : * @fops: [in] file operations for the new file
162 : * @priv: [in] private data for the new file (will be file's private_data)
163 : * @flags: [in] flags
164 : * @context_inode:
165 : * [in] the logical relationship with the new inode (optional)
166 : *
167 : * The LSM may use @context_inode in inode_init_security_anon(), but a
168 : * reference to it is not held. Returns the newly created file* or an error
169 : * pointer. See the anon_inode_getfile() documentation for more information.
170 : */
171 0 : struct file *anon_inode_getfile_secure(const char *name,
172 : const struct file_operations *fops,
173 : void *priv, int flags,
174 : const struct inode *context_inode)
175 : {
176 0 : return __anon_inode_getfile(name, fops, priv, flags,
177 : context_inode, true);
178 : }
179 :
180 0 : static int __anon_inode_getfd(const char *name,
181 : const struct file_operations *fops,
182 : void *priv, int flags,
183 : const struct inode *context_inode,
184 : bool secure)
185 : {
186 : int error, fd;
187 : struct file *file;
188 :
189 0 : error = get_unused_fd_flags(flags);
190 0 : if (error < 0)
191 : return error;
192 0 : fd = error;
193 :
194 0 : file = __anon_inode_getfile(name, fops, priv, flags, context_inode,
195 : secure);
196 0 : if (IS_ERR(file)) {
197 0 : error = PTR_ERR(file);
198 : goto err_put_unused_fd;
199 : }
200 0 : fd_install(fd, file);
201 :
202 0 : return fd;
203 :
204 : err_put_unused_fd:
205 0 : put_unused_fd(fd);
206 0 : return error;
207 : }
208 :
209 : /**
210 : * anon_inode_getfd - creates a new file instance by hooking it up to
211 : * an anonymous inode and a dentry that describe
212 : * the "class" of the file
213 : *
214 : * @name: [in] name of the "class" of the new file
215 : * @fops: [in] file operations for the new file
216 : * @priv: [in] private data for the new file (will be file's private_data)
217 : * @flags: [in] flags
218 : *
219 : * Creates a new file by hooking it on a single inode. This is
220 : * useful for files that do not need to have a full-fledged inode in
221 : * order to operate correctly. All the files created with
222 : * anon_inode_getfd() will use the same singleton inode, reducing
223 : * memory use and avoiding code duplication for the file/inode/dentry
224 : * setup. Returns a newly created file descriptor or an error code.
225 : */
226 0 : int anon_inode_getfd(const char *name, const struct file_operations *fops,
227 : void *priv, int flags)
228 : {
229 0 : return __anon_inode_getfd(name, fops, priv, flags, NULL, false);
230 : }
231 : EXPORT_SYMBOL_GPL(anon_inode_getfd);
232 :
233 : /**
234 : * anon_inode_getfd_secure - Like anon_inode_getfd(), but creates a new
235 : * !S_PRIVATE anon inode rather than reuse the singleton anon inode, and calls
236 : * the inode_init_security_anon() LSM hook. This allows the inode to have its
237 : * own security context and for a LSM to reject creation of the inode.
238 : *
239 : * @name: [in] name of the "class" of the new file
240 : * @fops: [in] file operations for the new file
241 : * @priv: [in] private data for the new file (will be file's private_data)
242 : * @flags: [in] flags
243 : * @context_inode:
244 : * [in] the logical relationship with the new inode (optional)
245 : *
246 : * The LSM may use @context_inode in inode_init_security_anon(), but a
247 : * reference to it is not held.
248 : */
249 0 : int anon_inode_getfd_secure(const char *name, const struct file_operations *fops,
250 : void *priv, int flags,
251 : const struct inode *context_inode)
252 : {
253 0 : return __anon_inode_getfd(name, fops, priv, flags, context_inode, true);
254 : }
255 : EXPORT_SYMBOL_GPL(anon_inode_getfd_secure);
256 :
257 1 : static int __init anon_inode_init(void)
258 : {
259 1 : anon_inode_mnt = kern_mount(&anon_inode_fs_type);
260 2 : if (IS_ERR(anon_inode_mnt))
261 0 : panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
262 :
263 1 : anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
264 2 : if (IS_ERR(anon_inode_inode))
265 0 : panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
266 :
267 1 : return 0;
268 : }
269 :
270 : fs_initcall(anon_inode_init);
271 :
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