// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/anon_inodes.c
*
* Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
*
* Thanks to Arnd Bergmann for code review and suggestions.
* More changes for Thomas Gleixner suggestions.
*
*/
#include <linux/cred.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/magic.h>
#include <linux/anon_inodes.h>
#include <linux/pseudo_fs.h>
#include <linux/uaccess.h>
static struct vfsmount *anon_inode_mnt __read_mostly;
static struct inode *anon_inode_inode;
/*
* anon_inodefs_dname() is called from d_path().
*/
static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
{
return dynamic_dname(dentry, buffer, buflen, "anon_inode:%s",
dentry->d_name.name);
}
static const struct dentry_operations anon_inodefs_dentry_operations = {
.d_dname = anon_inodefs_dname,
};
static int anon_inodefs_init_fs_context(struct fs_context *fc)
{
struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC);
if (!ctx)
return -ENOMEM;
ctx->dops = &anon_inodefs_dentry_operations;
return 0;
}
static struct file_system_type anon_inode_fs_type = {
.name = "anon_inodefs",
.init_fs_context = anon_inodefs_init_fs_context,
.kill_sb = kill_anon_super,
};
static struct inode *anon_inode_make_secure_inode(
const char *name,
const struct inode *context_inode)
{
struct inode *inode;
const struct qstr qname = QSTR_INIT(name, strlen(name));
int error;
inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
if (IS_ERR(inode))
return inode;
inode->i_flags &= ~S_PRIVATE;
error = security_inode_init_security_anon(inode, &qname, context_inode);
if (error) {
iput(inode);
return ERR_PTR(error);
}
return inode;
}
static struct file *__anon_inode_getfile(const char *name,
const struct file_operations *fops,
void *priv, int flags,
const struct inode *context_inode,
bool secure)
{
struct inode *inode;
struct file *file;
if (fops->owner && !try_module_get(fops->owner))
return ERR_PTR(-ENOENT);
if (secure) {
inode = anon_inode_make_secure_inode(name, context_inode);
if (IS_ERR(inode)) {
file = ERR_CAST(inode);
goto err;
}
} else {
inode = anon_inode_inode;
if (IS_ERR(inode)) {
file = ERR_PTR(-ENODEV);
goto err;
}
/*
* We know the anon_inode inode count is always
* greater than zero, so ihold() is safe.
*/
ihold(inode);
}
file = alloc_file_pseudo(inode, anon_inode_mnt, name,
flags & (O_ACCMODE | O_NONBLOCK), fops);
if (IS_ERR(file))
goto err_iput;
file->f_mapping = inode->i_mapping;
file->private_data = priv;
return file;
err_iput:
iput(inode);
err:
module_put(fops->owner);
return file;
}
/**
* anon_inode_getfile - creates a new file instance by hooking it up to an
* anonymous inode, and a dentry that describe the "class"
* of the file
*
* @name: [in] name of the "class" of the new file
* @fops: [in] file operations for the new file
* @priv: [in] private data for the new file (will be file's private_data)
* @flags: [in] flags
*
* Creates a new file by hooking it on a single inode. This is useful for files
* that do not need to have a full-fledged inode in order to operate correctly.
* All the files created with anon_inode_getfile() will share a single inode,
* hence saving memory and avoiding code duplication for the file/inode/dentry
* setup. Returns the newly created file* or an error pointer.
*/
struct file *anon_inode_getfile(const char *name,
const struct file_operations *fops,
void *priv, int flags)
{
return __anon_inode_getfile(name, fops, priv, flags, NULL, false);
}
EXPORT_SYMBOL_GPL(anon_inode_getfile);
/**
* anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new
* !S_PRIVATE anon inode rather than reuse the
* singleton anon inode and calls the
* inode_init_security_anon() LSM hook. This
* allows for both the inode to have its own
* security context and for the LSM to enforce
* policy on the inode's creation.
*
* @name: [in] name of the "class" of the new file
* @fops: [in] file operations for the new file
* @priv: [in] private data for the new file (will be file's private_data)
* @flags: [in] flags
* @context_inode:
* [in] the logical relationship with the new inode (optional)
*
* The LSM may use @context_inode in inode_init_security_anon(), but a
* reference to it is not held. Returns the newly created file* or an error
* pointer. See the anon_inode_getfile() documentation for more information.
*/
struct file *anon_inode_getfile_secure(const char *name,
const struct file_operations *fops,
void *priv, int flags,
const struct inode *context_inode)
{
return __anon_inode_getfile(name, fops, priv, flags,
context_inode, true);
}
static int __anon_inode_getfd(const char *name,
const struct file_operations *fops,
void *priv, int flags,
const struct inode *context_inode,
bool secure)
{
int error, fd;
struct file *file;
error = get_unused_fd_flags(flags);
if (error < 0)
return error;
fd = error;
file = __anon_inode_getfile(name, fops, priv, flags, context_inode,
secure);
if (IS_ERR(file)) {
error = PTR_ERR(file);
goto err_put_unused_fd;
}
fd_install(fd, file);
return fd;
err_put_unused_fd:
put_unused_fd(fd);
return error;
}
/**
* anon_inode_getfd - creates a new file instance by hooking it up to
* an anonymous inode and a dentry that describe
* the "class" of the file
*
* @name: [in] name of the "class" of the new file
* @fops: [in] file operations for the new file
* @priv: [in] private data for the new file (will be file's private_data)
* @flags: [in] flags
*
* Creates a new file by hooking it on a single inode. This is
* useful for files that do not need to have a full-fledged inode in
* order to operate correctly. All the files created with
* anon_inode_getfd() will use the same singleton inode, reducing
* memory use and avoiding code duplication for the file/inode/dentry
* setup. Returns a newly created file descriptor or an error code.
*/
int anon_inode_getfd(const char *name, const struct file_operations *fops,
void *priv, int flags)
{
return __anon_inode_getfd(name, fops, priv, flags, NULL, false);
}
EXPORT_SYMBOL_GPL(anon_inode_getfd);
/**
* anon_inode_getfd_secure - Like anon_inode_getfd(), but creates a new
* !S_PRIVATE anon inode rather than reuse the singleton anon inode, and calls
* the inode_init_security_anon() LSM hook. This allows the inode to have its
* own security context and for a LSM to reject creation of the inode.
*
* @name: [in] name of the "class" of the new file
* @fops: [in] file operations for the new file
* @priv: [in] private data for the new file (will be file's private_data)
* @flags: [in] flags
* @context_inode:
* [in] the logical relationship with the new inode (optional)
*
* The LSM may use @context_inode in inode_init_security_anon(), but a
* reference to it is not held.
*/
int anon_inode_getfd_secure(const char *name, const struct file_operations *fops,
void *priv, int flags,
const struct inode *context_inode)
{
return __anon_inode_getfd(name, fops, priv, flags, context_inode, true);
}
EXPORT_SYMBOL_GPL(anon_inode_getfd_secure);
static int __init anon_inode_init(void)
{
anon_inode_mnt = kern_mount(&anon_inode_fs_type);
if (IS_ERR(anon_inode_mnt))
panic("anon_inode_init() kernel mount failed (%ld)\n", PTR_ERR(anon_inode_mnt));
anon_inode_inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
if (IS_ERR(anon_inode_inode))
panic("anon_inode_init() inode allocation failed (%ld)\n", PTR_ERR(anon_inode_inode));
return 0;
}
fs_initcall(anon_inode_init);
