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/*
* security/tomoyo/realpath.c
*
* Pathname calculation functions for TOMOYO.
*
* Copyright (C) 2005-2010 NTT DATA CORPORATION
*/
#include <linux/types.h>
#include <linux/mount.h>
#include <linux/mnt_namespace.h>
#include <linux/fs_struct.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include "common.h"
/**
* tomoyo_encode: Convert binary string to ascii string.
*
* @buffer: Buffer for ASCII string.
* @buflen: Size of @buffer.
* @str: Binary string.
*
* Returns 0 on success, -ENOMEM otherwise.
*/
int tomoyo_encode(char *buffer, int buflen, const char *str)
{
while (1) {
const unsigned char c = *(unsigned char *) str++;
if (tomoyo_is_valid(c)) {
if (--buflen <= 0)
break;
*buffer++ = (char) c;
if (c != '\\')
continue;
if (--buflen <= 0)
break;
*buffer++ = (char) c;
continue;
}
if (!c) {
if (--buflen <= 0)
break;
*buffer = '\0';
return 0;
}
buflen -= 4;
if (buflen <= 0)
break;
*buffer++ = '\\';
*buffer++ = (c >> 6) + '0';
*buffer++ = ((c >> 3) & 7) + '0';
*buffer++ = (c & 7) + '0';
}
return -ENOMEM;
}
/**
* tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
*
* @path: Pointer to "struct path".
* @newname: Pointer to buffer to return value in.
* @newname_len: Size of @newname.
*
* Returns 0 on success, negative value otherwise.
*
* If dentry is a directory, trailing '/' is appended.
* Characters out of 0x20 < c < 0x7F range are converted to
* \ooo style octal string.
* Character \ is converted to \\ string.
*/
int tomoyo_realpath_from_path2(struct path *path, char *newname,
int newname_len)
{
int error = -ENOMEM;
struct dentry *dentry = path->dentry;
char *sp;
if (!dentry || !path->mnt || !newname || newname_len <= 2048)
return -EINVAL;
if (dentry->d_op && dentry->d_op->d_dname) {
/* For "socket:[\$]" and "pipe:[\$]". */
static const int offset = 1536;
sp = dentry->d_op->d_dname(dentry, newname + offset,
newname_len - offset);
} else {
struct path ns_root = {.mnt = NULL, .dentry = NULL};
spin_lock(&dcache_lock);
/* go to whatever namespace root we are under */
sp = __d_path(path, &ns_root, newname, newname_len);
spin_unlock(&dcache_lock);
/* Prepend "/proc" prefix if using internal proc vfs mount. */
if (!IS_ERR(sp) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
(path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) {
sp -= 5;
if (sp >= newname)
memcpy(sp, "/proc", 5);
else
sp = ERR_PTR(-ENOMEM);
}
}
if (IS_ERR(sp))
error = PTR_ERR(sp);
else
error = tomoyo_encode(newname, sp - newname, sp);
/* Append trailing '/' if dentry is a directory. */
if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
&& *newname) {
sp = newname + strlen(newname);
if (*(sp - 1) != '/') {
if (sp < newname + newname_len - 4) {
*sp++ = '/';
*sp = '\0';
} else {
error = -ENOMEM;
}
}
}
if (error)
tomoyo_warn_oom(__func__);
return error;
}
/**
* tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
*
* @path: Pointer to "struct path".
*
* Returns the realpath of the given @path on success, NULL otherwise.
*
* These functions use kzalloc(), so the caller must call kfree()
* if these functions didn't return NULL.
*/
char *tomoyo_realpath_from_path(struct path *path)
{
char *buf = kzalloc(sizeof(struct tomoyo_page_buffer), GFP_NOFS);
BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
<= TOMOYO_MAX_PATHNAME_LEN - 1);
if (!buf)
return NULL;
if (tomoyo_realpath_from_path2(path, buf,
TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
return buf;
kfree(buf);
return NULL;
}
/**
* tomoyo_realpath - Get realpath of a pathname.
*
* @pathname: The pathname to solve.
*
* Returns the realpath of @pathname on success, NULL otherwise.
*/
char *tomoyo_realpath(const char *pathname)
{
struct path path;
if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
char *buf = tomoyo_realpath_from_path(&path);
path_put(&path);
return buf;
}
return NULL;
}
/**
* tomoyo_realpath_nofollow - Get realpath of a pathname.
*
* @pathname: The pathname to solve.
*
* Returns the realpath of @pathname on success, NULL otherwise.
*/
char *tomoyo_realpath_nofollow(const char *pathname)
{
struct path path;
if (pathname && kern_path(pathname, 0, &path) == 0) {
char *buf = tomoyo_realpath_from_path(&path);
path_put(&path);
return buf;
}
return NULL;
}
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