/*
* AppArmor security module
*
* This file contains AppArmor function for pathnames
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/
#include <linux/magic.h>
#include <linux/mnt_namespace.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nsproxy.h>
#include <linux/path.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs_struct.h>
#include "include/apparmor.h"
#include "include/path.h"
#include "include/policy.h"
/* modified from dcache.c */
static int prepend(char **buffer, int buflen, const char *str, int namelen)
{
buflen -= namelen;
if (buflen < 0)
return -ENAMETOOLONG;
*buffer -= namelen;
memcpy(*buffer, str, namelen);
return 0;
}
#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
/**
* d_namespace_path - lookup a name associated with a given path
* @path: path to lookup (NOT NULL)
* @buf: buffer to store path to (NOT NULL)
* @buflen: length of @buf
* @name: Returns - pointer for start of path name with in @buf (NOT NULL)
* @flags: flags controlling path lookup
*
* Handle path name lookup.
*
* Returns: %0 else error code if path lookup fails
* When no error the path name is returned in @name which points to
* to a position in @buf
*/
static int d_namespace_path(struct path *path, char *buf, int buflen,
char **name, int flags)
{
struct path root, tmp;
char *res;
int deleted, connected;
int error = 0;
/* Get the root we want to resolve too */
if (flags & PATH_CHROOT_REL) {
/* resolve paths relative to chroot */
read_lock(¤t->fs->lock);
root = current->fs->root;
/* released below */
path_get(&root);
read_unlock(¤t->fs->lock);
} else {
/* resolve paths relative to namespace */
root.mnt = current->nsproxy->mnt_ns->root;
root.dentry = root.mnt->mnt_root;
/* released below */
path_get(&root);
}
spin_lock(&dcache_lock);
/* There is a race window between path lookup here and the
* need to strip the " (deleted) string that __d_path applies
* Detect the race and relookup the path
*
* The stripping of (deleted) is a hack that could be removed
* with an updated __d_path
*/
do {
tmp = root;
deleted = d_unlinked(path->dentry);
res = __d_path(path, &tmp, buf, buflen);
} while (deleted != d_unlinked(path->dentry));
spin_unlock(&dcache_lock);
*name = res;
/* handle error conditions - and still allow a partial path to
* be returned.
*/
if (IS_ERR(res)) {
error = PTR_ERR(res);
*name = buf;
goto out;
}
if (deleted) {
/* On some filesystems, newly allocated dentries appear to the
* security_path hooks as a deleted dentry except without an
* inode allocated.
*
* Remove the appended deleted text and return as string for
* normal mediation, or auditing. The (deleted) string is
* guaranteed to be added in this case, so just strip it.
*/
buf[buflen - 11] = 0; /* - (len(" (deleted)") +\0) */
if (path->dentry->d_inode && !(flags & PATH_MEDIATE_DELETED)) {
error = -ENOENT;
goto out;
}
}
/* Determine if the path is connected to the expected root */
connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt;
/* If the path is not connected,
* check if it is a sysctl and handle specially else remove any
* leading / that __d_path may have returned.
* Unless
* specifically directed to connect the path,
* OR
* if in a chroot and doing chroot relative paths and the path
* resolves to the namespace root (would be connected outside
* of chroot) and specifically directed to connect paths to
* namespace root.
*/
if (!connected) {
/* is the disconnect path a sysctl? */
if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
strncmp(*name, "/sys/", 5) == 0) {
/* TODO: convert over to using a per namespace
* control instead of hard coded /proc
*/
error = prepend(name, *name - buf, "/proc", 5);
} else if (!(flags & PATH_CONNECT_PATH) &&
!(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
(tmp.mnt == current->nsproxy->mnt_ns->root &&
tmp.dentry == tmp.mnt->mnt_root))) {
/* disconnected path, don't return pathname starting
* with '/'
*/
error = -ESTALE;
if (*res == '/')
*name = res + 1;
}
}
out:
path_put(&root);
return error;
}
/**
* get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
* @path: path to get name for (NOT NULL)
* @flags: flags controlling path lookup
* @buffer: buffer to put name in (NOT NULL)
* @size: size of buffer
* @name: Returns - contains position of path name in @buffer (NOT NULL)
*
* Returns: %0 else error on failure
*/
static int get_name_to_buffer(struct path *path, int flags, char *buffer,
int size, char **name)
{
int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
int error = d_namespace_path(path, buffer, size - adjust, name, flags);
if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
/*
* Append "/" to the pathname. The root directory is a special
* case; it already ends in slash.
*/
strcpy(&buffer[size - 2], "/");
return error;
}
/**
* aa_get_name - compute the pathname of a file
* @path: path the file (NOT NULL)
* @flags: flags controlling path name generation
* @buffer: buffer that aa_get_name() allocated (NOT NULL)
* @name: Returns - the generated path name if !error (NOT NULL)
*
* @name is a pointer to the beginning of the pathname (which usually differs
* from the beginning of the buffer), or NULL. If there is an error @name
* may contain a partial or invalid name that can be used for audit purposes,
* but it can not be used for mediation.
*
* We need PATH_IS_DIR to indicate whether the file is a directory or not
* because the file may not yet exist, and so we cannot check the inode's
* file type.
*
* Returns: %0 else error code if could retrieve name
*/
int aa_get_name(struct path *path, int flags, char **buffer, const char **name)
{
char *buf, *str = NULL;
int size = 256;
int error;
*name = NULL;
*buffer = NULL;
for (;;) {
/* freed by caller */
buf = kmalloc(size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
error = get_name_to_buffer(path, flags, buf, size, &str);
if (error != -ENAMETOOLONG)
break;
kfree(buf);
size <<= 1;
if (size > aa_g_path_max)
return -ENAMETOOLONG;
}
*buffer = buf;
*name = str;
return error;
}
