1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
7 * Thanks to Arnd Bergmann for code review and suggestions.
8 * More changes for Thomas Gleixner suggestions.
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>
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>
25 #include <linux/uaccess.h>
27 static struct vfsmount
*anon_inode_mnt __read_mostly
;
28 static struct inode
*anon_inode_inode
;
31 * anon_inodefs_dname() is called from d_path().
33 static char *anon_inodefs_dname(struct dentry
*dentry
, char *buffer
, int buflen
)
35 return dynamic_dname(dentry
, buffer
, buflen
, "anon_inode:%s",
39 static const struct dentry_operations anon_inodefs_dentry_operations
= {
40 .d_dname
= anon_inodefs_dname
,
43 static int anon_inodefs_init_fs_context(struct fs_context
*fc
)
45 struct pseudo_fs_context
*ctx
= init_pseudo(fc
, ANON_INODE_FS_MAGIC
);
48 ctx
->dops
= &anon_inodefs_dentry_operations
;
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
,
58 static struct inode
*anon_inode_make_secure_inode(
60 const struct inode
*context_inode
)
63 const struct qstr qname
= QSTR_INIT(name
, strlen(name
));
66 inode
= alloc_anon_inode(anon_inode_mnt
->mnt_sb
);
69 inode
->i_flags
&= ~S_PRIVATE
;
70 error
= security_inode_init_security_anon(inode
, &qname
, context_inode
);
73 return ERR_PTR(error
);
78 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
,
87 if (fops
->owner
&& !try_module_get(fops
->owner
))
88 return ERR_PTR(-ENOENT
);
91 inode
= anon_inode_make_secure_inode(name
, context_inode
);
93 file
= ERR_CAST(inode
);
97 inode
= anon_inode_inode
;
99 file
= ERR_PTR(-ENODEV
);
103 * We know the anon_inode inode count is always
104 * greater than zero, so ihold() is safe.
109 file
= alloc_file_pseudo(inode
, anon_inode_mnt
, name
,
110 flags
& (O_ACCMODE
| O_NONBLOCK
), fops
);
114 file
->f_mapping
= inode
->i_mapping
;
116 file
->private_data
= priv
;
123 module_put(fops
->owner
);
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"
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)
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.
143 struct file
*anon_inode_getfile(const char *name
,
144 const struct file_operations
*fops
,
145 void *priv
, int flags
)
147 return __anon_inode_getfile(name
, fops
, priv
, flags
, NULL
, false);
149 EXPORT_SYMBOL_GPL(anon_inode_getfile
);
151 static int __anon_inode_getfd(const char *name
,
152 const struct file_operations
*fops
,
153 void *priv
, int flags
,
154 const struct inode
*context_inode
,
160 error
= get_unused_fd_flags(flags
);
165 file
= __anon_inode_getfile(name
, fops
, priv
, flags
, context_inode
,
168 error
= PTR_ERR(file
);
169 goto err_put_unused_fd
;
171 fd_install(fd
, file
);
181 * anon_inode_getfd - creates a new file instance by hooking it up to
182 * an anonymous inode and a dentry that describe
183 * the "class" of the file
185 * @name: [in] name of the "class" of the new file
186 * @fops: [in] file operations for the new file
187 * @priv: [in] private data for the new file (will be file's private_data)
190 * Creates a new file by hooking it on a single inode. This is
191 * useful for files that do not need to have a full-fledged inode in
192 * order to operate correctly. All the files created with
193 * anon_inode_getfd() will use the same singleton inode, reducing
194 * memory use and avoiding code duplication for the file/inode/dentry
195 * setup. Returns a newly created file descriptor or an error code.
197 int anon_inode_getfd(const char *name
, const struct file_operations
*fops
,
198 void *priv
, int flags
)
200 return __anon_inode_getfd(name
, fops
, priv
, flags
, NULL
, false);
202 EXPORT_SYMBOL_GPL(anon_inode_getfd
);
205 * anon_inode_getfd_secure - Like anon_inode_getfd(), but creates a new
206 * !S_PRIVATE anon inode rather than reuse the singleton anon inode, and calls
207 * the inode_init_security_anon() LSM hook. This allows the inode to have its
208 * own security context and for a LSM to reject creation of the inode.
210 * @name: [in] name of the "class" of the new file
211 * @fops: [in] file operations for the new file
212 * @priv: [in] private data for the new file (will be file's private_data)
215 * [in] the logical relationship with the new inode (optional)
217 * The LSM may use @context_inode in inode_init_security_anon(), but a
218 * reference to it is not held.
220 int anon_inode_getfd_secure(const char *name
, const struct file_operations
*fops
,
221 void *priv
, int flags
,
222 const struct inode
*context_inode
)
224 return __anon_inode_getfd(name
, fops
, priv
, flags
, context_inode
, true);
226 EXPORT_SYMBOL_GPL(anon_inode_getfd_secure
);
228 static int __init
anon_inode_init(void)
230 anon_inode_mnt
= kern_mount(&anon_inode_fs_type
);
231 if (IS_ERR(anon_inode_mnt
))
232 panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt
));
234 anon_inode_inode
= alloc_anon_inode(anon_inode_mnt
->mnt_sb
);
235 if (IS_ERR(anon_inode_inode
))
236 panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode
));
241 fs_initcall(anon_inode_init
);