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[PATCH] add securityfs for all LSMs to use
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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 <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
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gregkh authored and Chris Wright committed Jul 9, 2005
1 parent 043d051 commit b67dbf9
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5 changes: 5 additions & 0 deletions include/linux/security.h
Original file line number Diff line number Diff line change
Expand Up @@ -1983,6 +1983,11 @@ extern int register_security (struct security_operations *ops);
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 */
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2 changes: 1 addition & 1 deletion security/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ obj-y += commoncap.o
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
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347 changes: 347 additions & 0 deletions security/inode.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,347 @@
/*
* inode.c - securityfs
*
* Copyright (C) 2005 Greg Kroah-Hartman <[email protected]>
*
* 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 <[email protected]>
* 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");

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