// SPDX-License-Identifier: GPL-2.0
/*
* security/tomoyo/realpath.c
*
* Copyright (C) 2005-2011 NTT DATA CORPORATION
*/
#include "common.h"
#include <linux/magic.h>
#include <linux/proc_fs.h>
/**
* tomoyo_encode2 - Encode binary string to ascii string.
*
* @str: String in binary format.
* @str_len: Size of @str in byte.
*
* Returns pointer to @str in ascii format on success, NULL otherwise.
*
* This function uses kzalloc(), so caller must kfree() if this function
* didn't return NULL.
*/
char *tomoyo_encode2(const char *str, int str_len)
{
int i;
int len = 0;
const char *p = str;
char *cp;
char *cp0;
if (!p)
return NULL;
for (i = 0; i < str_len; i++) {
const unsigned char c = p[i];
if (c == '\\')
len += 2;
else if (c > ' ' && c < 127)
len++;
else
len += 4;
}
len++;
/* Reserve space for appending "/". */
cp = kzalloc(len + 10, GFP_NOFS);
if (!cp)
return NULL;
cp0 = cp;
p = str;
for (i = 0; i < str_len; i++) {
const unsigned char c = p[i];
if (c == '\\') {
*cp++ = '\\';
*cp++ = '\\';
} else if (c > ' ' && c < 127) {
*cp++ = c;
} else {
*cp++ = '\\';
*cp++ = (c >> 6) + '0';
*cp++ = ((c >> 3) & 7) + '0';
*cp++ = (c & 7) + '0';
}
}
return cp0;
}
/**
* tomoyo_encode - Encode binary string to ascii string.
*
* @str: String in binary format.
*
* Returns pointer to @str in ascii format on success, NULL otherwise.
*
* This function uses kzalloc(), so caller must kfree() if this function
* didn't return NULL.
*/
char *tomoyo_encode(const char *str)
{
return str ? tomoyo_encode2(str, strlen(str)) : NULL;
}
/**
* tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
*
* @path: Pointer to "struct path".
* @buffer: Pointer to buffer to return value in.
* @buflen: Sizeof @buffer.
*
* Returns the buffer on success, an error code otherwise.
*
* If dentry is a directory, trailing '/' is appended.
*/
static char *tomoyo_get_absolute_path(const struct path *path, char * const buffer,
const int buflen)
{
char *pos = ERR_PTR(-ENOMEM);
if (buflen >= 256) {
/* go to whatever namespace root we are under */
pos = d_absolute_path(path, buffer, buflen - 1);
if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
struct inode *inode = d_backing_inode(path->dentry);
if (inode && S_ISDIR(inode->i_mode)) {
buffer[buflen - 2] = '/';
buffer[buflen - 1] = '\0';
}
}
}
return pos;
}
/**
* tomoyo_get_dentry_path - Get the path of a dentry.
*
* @dentry: Pointer to "struct dentry".
* @buffer: Pointer to buffer to return value in.
* @buflen: Sizeof @buffer.
*
* Returns the buffer on success, an error code otherwise.
*
* If dentry is a directory, trailing '/' is appended.
*/
static char *tomoyo_get_dentry_path(struct dentry *dentry, char * const buffer,
const int buflen)
{
char *pos = ERR_PTR(-ENOMEM);
if (buflen >= 256) {
pos = dentry_path_raw(dentry, buffer, buflen - 1);
if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
struct inode *inode = d_backing_inode(dentry);
if (inode && S_ISDIR(inode->i_mode)) {
buffer[buflen - 2] = '/';
buffer[buflen - 1] = '\0';
}
}
}
return pos;
}
/**
* tomoyo_get_local_path - Get the path of a dentry.
*
* @dentry: Pointer to "struct dentry".
* @buffer: Pointer to buffer to return value in.
* @buflen: Sizeof @buffer.
*
* Returns the buffer on success, an error code otherwise.
*/
static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
const int buflen)
{
struct super_block *sb = dentry->d_sb;
char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);
if (IS_ERR(pos))
return pos;
/* Convert from $PID to self if $PID is current thread. */
if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
char *ep;
const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
struct pid_namespace *proc_pidns = proc_pid_ns(sb);
if (*ep == '/' && pid && pid ==
task_tgid_nr_ns(current, proc_pidns)) {
pos = ep - 5;
if (pos < buffer)
goto out;
memmove(pos, "/self", 5);
}
goto prepend_filesystem_name;
}
/* Use filesystem name for unnamed devices. */
if (!MAJOR(sb->s_dev))
goto prepend_filesystem_name;
{
struct inode *inode = d_backing_inode(sb->s_root);
/*
* Use filesystem name if filesystem does not support rename()
* operation.
*/
if (!inode->i_op->rename)
goto prepend_filesystem_name;
}
/* Prepend device name. */
{
char name[64];
int name_len;
const dev_t dev = sb->s_dev;
name[sizeof(name) - 1] = '\0';
snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
MINOR(dev));
name_len = strlen(name);
pos -= name_len;
if (pos < buffer)
goto out;
memmove(pos, name, name_len);
return pos;
}
/* Prepend filesystem name. */
prepend_filesystem_name:
{
const char *name = sb->s_type->name;
const int name_len = strlen(name);
pos -= name_len + 1;
if (pos < buffer)
goto out;
memmove(pos, name, name_len);
pos[name_len] = ':';
}
return pos;
out:
return ERR_PTR(-ENOMEM);
}
/**
* 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.
*
* 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.
*
* These functions use kzalloc(), so the caller must call kfree()
* if these functions didn't return NULL.
*/
char *tomoyo_realpath_from_path(const struct path *path)
{
char *buf = NULL;
char *name = NULL;
unsigned int buf_len = PAGE_SIZE / 2;
struct dentry *dentry = path->dentry;
struct super_block *sb = dentry->d_sb;
while (1) {
char *pos;
struct inode *inode;
buf_len <<= 1;
kfree(buf);
buf = kmalloc(buf_len, GFP_NOFS);
if (!buf)
break;
/* To make sure that pos is '\0' terminated. */
buf[buf_len - 1] = '\0';
/* For "pipe:[\$]" and "socket:[\$]". */
if (dentry->d_op && dentry->d_op->d_dname) {
pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
goto encode;
}
inode = d_backing_inode(sb->s_root);
/*
* Get local name for filesystems without rename() operation
*/
if ((!inode->i_op->rename &&
!(sb->s_type->fs_flags & FS_REQUIRES_DEV)))
pos = tomoyo_get_local_path(path->dentry, buf,
buf_len - 1);
/* Get absolute name for the rest. */
else {
pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
/*
* Fall back to local name if absolute name is not
* available.
*/
if (pos == ERR_PTR(-EINVAL))
pos = tomoyo_get_local_path(path->dentry, buf,
buf_len - 1);
}
encode:
if (IS_ERR(pos))
continue;
name = tomoyo_encode(pos);
break;
}
kfree(buf);
if (!name)
tomoyo_warn_oom(__func__);
return name;
}
/**
* 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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