anon_inodes.c | Explore in Territory

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  fs/anon_inodes.c
 *
 *  Copyright (C) 2007  Davide Libenzi <[email protected]>
 *
 *  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 __ro_after_init;
static struct inode *anon_inode_inode __ro_after_init;

/*
 * anon_inodefs_dname() is called from d_path().
 */
static char *anon_inodefs_dname(struct dentry *dentry, char *buffer, int buflen)
{ … }

static const struct dentry_operations anon_inodefs_dentry_operations = …;

static int anon_inodefs_init_fs_context(struct fs_context *fc)
{ … }

static struct file_system_type anon_inode_fs_type = …;

static struct inode *anon_inode_make_secure_inode(
	const char *name,
	const struct inode *context_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 make_inode)
{ … }

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * anon_inode_getfile_fmode - 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
 * @f_mode:  [in]    fmode
 *
 * 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. Allows setting the fmode. Returns the newly created file* or an error
 * pointer.
 */
struct file *anon_inode_getfile_fmode(const char *name,
				const struct file_operations *fops,
				void *priv, int flags, fmode_t f_mode)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * anon_inode_create_getfile - 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.
 *
 * @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)
 *
 * Create a new anonymous inode and file pair.  This can be done for two
 * reasons:
 *
 * - for the inode to have its own security context, so that LSMs can enforce
 *   policy on the inode's creation;
 *
 * - if the caller needs a unique inode, for example in order to customize
 *   the size returned by fstat()
 *
 * 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.
 */
struct file *anon_inode_create_getfile(const char *name,
				       const struct file_operations *fops,
				       void *priv, int flags,
				       const struct inode *context_inode)
{ … }
EXPORT_SYMBOL_GPL(…);

static int __anon_inode_getfd(const char *name,
			      const struct file_operations *fops,
			      void *priv, int flags,
			      const struct inode *context_inode,
			      bool make_inode)
{ … }

/**
 * 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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * anon_inode_create_getfd - 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.
 *
 * @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)
 *
 * Create a new anonymous inode and file pair.  This can be done for two
 * reasons:
 *
 * - for the inode to have its own security context, so that LSMs can enforce
 *   policy on the inode's creation;
 *
 * - if the caller needs a unique inode, for example in order to customize
 *   the size returned by fstat()
 *
 * The LSM may use @context_inode in inode_init_security_anon(), but a
 * reference to it is not held.
 *
 * Returns a newly created file descriptor or an error code.
 */
int anon_inode_create_getfd(const char *name, const struct file_operations *fops,
			    void *priv, int flags,
			    const struct inode *context_inode)
{ … }


static int __init anon_inode_init(void)
{ … }

fs_initcall(anon_inode_init);
linux/fs/anon_inodes.c
