[PATCH] add securityfs for all LSMs to use

Greg KH
2005-07-07T21:40:46Z

Here's a small patch against 2.6.13-rc2 that adds securityfs, a virtual
fs that all LSMs can use instead of creating their own. The fs should
be mounted at /sys/kernel/security, and the fs creates that mount point.
This will make the LSB people happy that we aren't creating a new
/my_lsm_fs directory in the root for every different LSM.

It has changed a bit since the last version, thanks to comments from
Mike Waychison.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/security.h | 5
security/Makefile | 2
security/inode.c | 347 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 353 insertions(+), 1 deletion(-)

--- gregkh-2.6.orig/security/Makefile 2005-07-07 14:24:41.000000000 -0700
+++ gregkh-2.6/security/Makefile 2005-07-07 14:24:46.000000000 -0700
@@ -11,7 +11,7 @@
endif

# Object file lists
-obj-$(CONFIG_SECURITY) += security.o dummy.o
+obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o
# Must precede capability.o in order to stack properly.
obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o
obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gregkh-2.6/security/inode.c 2005-07-07 14:31:55.000000000 -0700
@@ -0,0 +1,347 @@
+/*
+ * inode.c - securityfs
+ *
+ * Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * Based on fs/debugfs/inode.c which had the following copyright notice:
+ * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
+ * Copyright (C) 2004 IBM Inc.
+ */
+
+/* #define DEBUG */
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/namei.h>
+#include <linux/security.h>
+
+#define SECURITYFS_MAGIC 0x73636673
+
+static struct vfsmount *mount;
+static int mount_count;
+
+/*
+ * TODO:
+ * I think I can get rid of these default_file_ops, but not quite sure...
+ */
+static ssize_t default_read_file(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return 0;
+}
+
+static ssize_t default_write_file(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ return count;
+}
+
+static int default_open(struct inode *inode, struct file *file)
+{
+ if (inode->u.generic_ip)
+ file->private_data = inode->u.generic_ip;
+
+ return 0;
+}
+
+static struct file_operations default_file_ops = {
+ .read = default_read_file,
+ .write = default_write_file,
+ .open = default_open,
+};
+
+static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
+{
+ struct inode *inode = new_inode(sb);
+
+ if (inode) {
+ inode->i_mode = mode;
+ inode->i_uid = 0;
+ inode->i_gid = 0;
+ inode->i_blksize = PAGE_CACHE_SIZE;
+ inode->i_blocks = 0;
+ inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ switch (mode & S_IFMT) {
+ default:
+ init_special_inode(inode, mode, dev);
+ break;
+ case S_IFREG:
+ inode->i_fop = &default_file_ops;
+ break;
+ case S_IFDIR:
+ inode->i_op = &simple_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+
+ /* directory inodes start off with i_nlink == 2 (for "." entry) */
+ inode->i_nlink++;
+ break;
+ }
+ }
+ return inode;
+}
+
+/* SMP-safe */
+static int mknod(struct inode *dir, struct dentry *dentry,
+ int mode, dev_t dev)
+{
+ struct inode *inode;
+ int error = -EPERM;
+
+ if (dentry->d_inode)
+ return -EEXIST;
+
+ inode = get_inode(dir->i_sb, mode, dev);
+ if (inode) {
+ d_instantiate(dentry, inode);
+ dget(dentry);
+ error = 0;
+ }
+ return error;
+}
+
+static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+ int res;
+
+ mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
+ res = mknod(dir, dentry, mode, 0);
+ if (!res)
+ dir->i_nlink++;
+ return res;
+}
+
+static int create(struct inode *dir, struct dentry *dentry, int mode)
+{
+ mode = (mode & S_IALLUGO) | S_IFREG;
+ return mknod(dir, dentry, mode, 0);
+}
+
+static inline int positive(struct dentry *dentry)
+{
+ return dentry->d_inode && !d_unhashed(dentry);
+}
+
+static int fill_super(struct super_block *sb, void *data, int silent)
+{
+ static struct tree_descr files[] = {{""}};
+
+ return simple_fill_super(sb, SECURITYFS_MAGIC, files);
+}
+
+static struct super_block *get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name,
+ void *data)
+{
+ return get_sb_single(fs_type, flags, data, fill_super);
+}
+
+static struct file_system_type fs_type = {
+ .owner = THIS_MODULE,
+ .name = "securityfs",
+ .get_sb = get_sb,
+ .kill_sb = kill_litter_super,
+};
+
+static int create_by_name(const char *name, mode_t mode,
+ struct dentry *parent,
+ struct dentry **dentry)
+{
+ int error = 0;
+
+ *dentry = NULL;
+
+ /* If the parent is not specified, we create it in the root.
+ * We need the root dentry to do this, which is in the super
+ * block. A pointer to that is in the struct vfsmount that we
+ * have around.
+ */
+ if (!parent ) {
+ if (mount && mount->mnt_sb) {
+ parent = mount->mnt_sb->s_root;
+ }
+ }
+ if (!parent) {
+ pr_debug("securityfs: Ah! can not find a parent!\n");
+ return -EFAULT;
+ }
+
+ down(&parent->d_inode->i_sem);
+ *dentry = lookup_one_len(name, parent, strlen(name));
+ if (!IS_ERR(dentry)) {
+ if ((mode & S_IFMT) == S_IFDIR)
+ error = mkdir(parent->d_inode, *dentry, mode);
+ else
+ error = create(parent->d_inode, *dentry, mode);
+ } else
+ error = PTR_ERR(dentry);
+ up(&parent->d_inode->i_sem);
+
+ return error;
+}
+
+/**
+ * securityfs_create_file - create a file in the securityfs filesystem
+ *
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this paramater is NULL, then the
+ * file will be created in the root of the securityfs filesystem.
+ * @data: a pointer to something that the caller will want to get to later
+ * on. The inode.u.generic_ip pointer will point to this value on
+ * the open() call.
+ * @fops: a pointer to a struct file_operations that should be used for
+ * this file.
+ *
+ * This is the basic "create a file" function for securityfs. It allows for a
+ * wide range of flexibility in createing a file, or a directory (if you
+ * want to create a directory, the securityfs_create_dir() function is
+ * recommended to be used instead.)
+ *
+ * This function will return a pointer to a dentry if it succeeds. This
+ * pointer must be passed to the securityfs_remove() function when the file is
+ * to be removed (no automatic cleanup happens if your module is unloaded,
+ * you are responsible here.) If an error occurs, NULL will be returned.
+ *
+ * If securityfs is not enabled in the kernel, the value -ENODEV will be
+ * returned. It is not wise to check for this value, but rather, check for
+ * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
+ * code.
+ */
+struct dentry *securityfs_create_file(const char *name, mode_t mode,
+ struct dentry *parent, void *data,
+ struct file_operations *fops)
+{
+ struct dentry *dentry = NULL;
+ int error;
+
+ pr_debug("securityfs: creating file '%s'\n",name);
+
+ error = simple_pin_fs("securityfs", &mount, &mount_count);
+ if (error) {
+ dentry = ERR_PTR(error);
+ goto exit;
+ }
+
+ error = create_by_name(name, mode, parent, &dentry);
+ if (error) {
+ dentry = ERR_PTR(error);
+ simple_release_fs(&mount, &mount_count);
+ goto exit;
+ }
+
+ if (dentry->d_inode) {
+ if (fops)
+ dentry->d_inode->i_fop = fops;
+ if (data)
+ dentry->d_inode->u.generic_ip = data;
+ }
+exit:
+ return dentry;
+}
+EXPORT_SYMBOL_GPL(securityfs_create_file);
+
+/**
+ * securityfs_create_dir - create a directory in the securityfs filesystem
+ *
+ * @name: a pointer to a string containing the name of the directory to
+ * create.
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this paramater is NULL, then the
+ * directory will be created in the root of the securityfs filesystem.
+ *
+ * This function creates a directory in securityfs with the given name.
+ *
+ * This function will return a pointer to a dentry if it succeeds. This
+ * pointer must be passed to the securityfs_remove() function when the file is
+ * to be removed (no automatic cleanup happens if your module is unloaded,
+ * you are responsible here.) If an error occurs, NULL will be returned.
+ *
+ * If securityfs is not enabled in the kernel, the value -ENODEV will be
+ * returned. It is not wise to check for this value, but rather, check for
+ * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
+ * code.
+ */
+struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
+{
+ return securityfs_create_file(name,
+ S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
+ parent, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(securityfs_create_dir);
+
+/**
+ * securityfs_remove - removes a file or directory from the securityfs filesystem
+ *
+ * @dentry: a pointer to a the dentry of the file or directory to be
+ * removed.
+ *
+ * This function removes a file or directory in securityfs that was previously
+ * created with a call to another securityfs function (like
+ * securityfs_create_file() or variants thereof.)
+ *
+ * This function is required to be called in order for the file to be
+ * removed, no automatic cleanup of files will happen when a module is
+ * removed, you are responsible here.
+ */
+void securityfs_remove(struct dentry *dentry)
+{
+ struct dentry *parent;
+
+ if (!dentry)
+ return;
+
+ parent = dentry->d_parent;
+ if (!parent || !parent->d_inode)
+ return;
+
+ down(&parent->d_inode->i_sem);
+ if (positive(dentry)) {
+ if (dentry->d_inode) {
+ if (S_ISDIR(dentry->d_inode->i_mode))
+ simple_rmdir(parent->d_inode, dentry);
+ else
+ simple_unlink(parent->d_inode, dentry);
+ dput(dentry);
+ }
+ }
+ up(&parent->d_inode->i_sem);
+ simple_release_fs(&mount, &mount_count);
+}
+EXPORT_SYMBOL_GPL(securityfs_remove);
+
+static decl_subsys(security, NULL, NULL);
+
+static int __init securityfs_init(void)
+{
+ int retval;
+
+ kset_set_kset_s(&security_subsys, kernel_subsys);
+ retval = subsystem_register(&security_subsys);
+ if (retval)
+ return retval;
+
+ retval = register_filesystem(&fs_type);
+ if (retval)
+ subsystem_unregister(&security_subsys);
+ return retval;
+}
+
+static void __exit securityfs_exit(void)
+{
+ simple_release_fs(&mount, &mount_count);
+ unregister_filesystem(&fs_type);
+ subsystem_unregister(&security_subsys);
+}
+
+core_initcall(securityfs_init);
+module_exit(securityfs_exit);
+MODULE_LICENSE("GPL");
+
--- gregkh-2.6.orig/include/linux/security.h 2005-07-07 14:24:41.000000000 -0700
+++ gregkh-2.6/include/linux/security.h 2005-07-07 14:24:46.000000000 -0700
@@ -1983,6 +1983,11 @@
extern int unregister_security (struct security_operations *ops);
extern int mod_reg_security (const char *name, struct security_operations *ops);
extern int mod_unreg_security (const char *name, struct security_operations *ops);
+extern struct dentry *securityfs_create_file(const char *name, mode_t mode,
+ struct dentry *parent, void *data,
+ struct file_operations *fops);
+extern struct dentry *securityfs_create_dir(const char *name, struct dentry *parent);
+extern void securityfs_remove(struct dentry *dentry);

#else /* CONFIG_SECURITY */