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32 results

anon_inodes.c

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    Lukas Bulwahn authored and Paul Moore committed
    Commit e7e832ce ("fs: add LSM-supporting anon-inode interface") adds
    more kerneldoc description, but also a few new warnings on
    anon_inode_getfd_secure() due to missing parameter descriptions.
    
    Rephrase to appropriate kernel-doc for anon_inode_getfd_secure().
    
    Signed-off-by: default avatarLukas Bulwahn <lukas.bulwahn@gmail.com>
    Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
    365982ab
    History
    anon_inodes.c 6.77 KiB
    // 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);
    
    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);