// SPDX-License-Identifier: GPL-2.0
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/*
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* security/tomoyo/realpath.c
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*
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* Copyright (C) 2005-2011 NTT DATA CORPORATION
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*/
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#include "common.h"
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#include <linux/magic.h>
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#include <linux/proc_fs.h>
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/**
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* tomoyo_encode2 - Encode binary string to ascii string.
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*
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* @str: String in binary format.
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* @str_len: Size of @str in byte.
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*
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* Returns pointer to @str in ascii format on success, NULL otherwise.
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*
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* This function uses kzalloc(), so caller must kfree() if this function
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* didn't return NULL.
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*/
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char *tomoyo_encode2(const char *str, int str_len)
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{
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int i;
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int len = 0;
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const char *p = str;
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char *cp;
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char *cp0;
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if (!p)
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return NULL;
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for (i = 0; i < str_len; i++) {
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const unsigned char c = p[i];
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if (c == '\\')
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len += 2;
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else if (c > ' ' && c < 127)
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len++;
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else
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len += 4;
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}
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len++;
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/* Reserve space for appending "/". */
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cp = kzalloc(len + 10, GFP_NOFS);
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if (!cp)
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return NULL;
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cp0 = cp;
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p = str;
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for (i = 0; i < str_len; i++) {
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const unsigned char c = p[i];
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if (c == '\\') {
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*cp++ = '\\';
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*cp++ = '\\';
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} else if (c > ' ' && c < 127) {
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*cp++ = c;
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} else {
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*cp++ = '\\';
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*cp++ = (c >> 6) + '0';
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*cp++ = ((c >> 3) & 7) + '0';
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*cp++ = (c & 7) + '0';
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}
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}
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return cp0;
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}
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/**
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* tomoyo_encode - Encode binary string to ascii string.
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*
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* @str: String in binary format.
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*
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* Returns pointer to @str in ascii format on success, NULL otherwise.
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*
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* This function uses kzalloc(), so caller must kfree() if this function
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* didn't return NULL.
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*/
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char *tomoyo_encode(const char *str)
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{
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return str ? tomoyo_encode2(str, strlen(str)) : NULL;
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}
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/**
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* tomoyo_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
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*
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* @path: Pointer to "struct path".
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* @buffer: Pointer to buffer to return value in.
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* @buflen: Sizeof @buffer.
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*
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* Returns the buffer on success, an error code otherwise.
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*
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* If dentry is a directory, trailing '/' is appended.
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*/
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static char *tomoyo_get_absolute_path(const struct path *path, char * const buffer,
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const int buflen)
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{
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char *pos = ERR_PTR(-ENOMEM);
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if (buflen >= 256) {
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/* go to whatever namespace root we are under */
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pos = d_absolute_path(path, buffer, buflen - 1);
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if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
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struct inode *inode = d_backing_inode(path->dentry);
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if (inode && S_ISDIR(inode->i_mode)) {
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buffer[buflen - 2] = '/';
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buffer[buflen - 1] = '\0';
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}
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}
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}
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return pos;
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}
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/**
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* tomoyo_get_dentry_path - Get the path of a dentry.
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*
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* @dentry: Pointer to "struct dentry".
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* @buffer: Pointer to buffer to return value in.
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* @buflen: Sizeof @buffer.
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*
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* Returns the buffer on success, an error code otherwise.
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*
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* If dentry is a directory, trailing '/' is appended.
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*/
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static char *tomoyo_get_dentry_path(struct dentry *dentry, char * const buffer,
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const int buflen)
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{
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char *pos = ERR_PTR(-ENOMEM);
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if (buflen >= 256) {
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pos = dentry_path_raw(dentry, buffer, buflen - 1);
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if (!IS_ERR(pos) && *pos == '/' && pos[1]) {
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struct inode *inode = d_backing_inode(dentry);
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if (inode && S_ISDIR(inode->i_mode)) {
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buffer[buflen - 2] = '/';
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buffer[buflen - 1] = '\0';
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}
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}
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}
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return pos;
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}
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/**
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* tomoyo_get_local_path - Get the path of a dentry.
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*
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* @dentry: Pointer to "struct dentry".
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* @buffer: Pointer to buffer to return value in.
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* @buflen: Sizeof @buffer.
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*
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* Returns the buffer on success, an error code otherwise.
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*/
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static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
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const int buflen)
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{
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struct super_block *sb = dentry->d_sb;
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char *pos = tomoyo_get_dentry_path(dentry, buffer, buflen);
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if (IS_ERR(pos))
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return pos;
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/* Convert from $PID to self if $PID is current thread. */
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if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
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char *ep;
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const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
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struct pid_namespace *proc_pidns = proc_pid_ns(sb);
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if (*ep == '/' && pid && pid ==
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task_tgid_nr_ns(current, proc_pidns)) {
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pos = ep - 5;
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if (pos < buffer)
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goto out;
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memmove(pos, "/self", 5);
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}
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goto prepend_filesystem_name;
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}
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/* Use filesystem name for unnamed devices. */
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if (!MAJOR(sb->s_dev))
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goto prepend_filesystem_name;
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{
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struct inode *inode = d_backing_inode(sb->s_root);
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/*
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* Use filesystem name if filesystem does not support rename()
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* operation.
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*/
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if (!inode->i_op->rename)
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goto prepend_filesystem_name;
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}
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/* Prepend device name. */
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{
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char name[64];
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int name_len;
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const dev_t dev = sb->s_dev;
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name[sizeof(name) - 1] = '\0';
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snprintf(name, sizeof(name) - 1, "dev(%u,%u):", MAJOR(dev),
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MINOR(dev));
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name_len = strlen(name);
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pos -= name_len;
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if (pos < buffer)
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goto out;
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memmove(pos, name, name_len);
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return pos;
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}
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/* Prepend filesystem name. */
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prepend_filesystem_name:
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{
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const char *name = sb->s_type->name;
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const int name_len = strlen(name);
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pos -= name_len + 1;
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if (pos < buffer)
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goto out;
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memmove(pos, name, name_len);
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pos[name_len] = ':';
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}
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return pos;
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out:
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return ERR_PTR(-ENOMEM);
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}
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/**
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* tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
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*
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* @path: Pointer to "struct path".
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*
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* Returns the realpath of the given @path on success, NULL otherwise.
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*
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* If dentry is a directory, trailing '/' is appended.
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* Characters out of 0x20 < c < 0x7F range are converted to
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* \ooo style octal string.
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* Character \ is converted to \\ string.
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*
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* These functions use kzalloc(), so the caller must call kfree()
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* if these functions didn't return NULL.
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*/
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char *tomoyo_realpath_from_path(const struct path *path)
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{
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char *buf = NULL;
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char *name = NULL;
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unsigned int buf_len = PAGE_SIZE / 2;
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struct dentry *dentry = path->dentry;
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struct super_block *sb;
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if (!dentry)
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return NULL;
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sb = dentry->d_sb;
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while (1) {
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char *pos;
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struct inode *inode;
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buf_len <<= 1;
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kfree(buf);
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buf = kmalloc(buf_len, GFP_NOFS);
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if (!buf)
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break;
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/* To make sure that pos is '\0' terminated. */
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buf[buf_len - 1] = '\0';
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/* For "pipe:[\$]" and "socket:[\$]". */
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if (dentry->d_op && dentry->d_op->d_dname) {
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pos = dentry->d_op->d_dname(dentry, buf, buf_len - 1);
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goto encode;
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}
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inode = d_backing_inode(sb->s_root);
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/*
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* Get local name for filesystems without rename() operation
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* or dentry without vfsmount.
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*/
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if (!path->mnt ||
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(!inode->i_op->rename &&
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!(sb->s_type->fs_flags & FS_REQUIRES_DEV)))
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pos = tomoyo_get_local_path(path->dentry, buf,
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buf_len - 1);
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/* Get absolute name for the rest. */
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else {
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pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
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/*
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* Fall back to local name if absolute name is not
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* available.
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*/
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if (pos == ERR_PTR(-EINVAL))
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pos = tomoyo_get_local_path(path->dentry, buf,
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buf_len - 1);
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}
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encode:
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if (IS_ERR(pos))
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continue;
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name = tomoyo_encode(pos);
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break;
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}
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kfree(buf);
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if (!name)
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tomoyo_warn_oom(__func__);
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return name;
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}
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/**
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* tomoyo_realpath_nofollow - Get realpath of a pathname.
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*
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* @pathname: The pathname to solve.
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*
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* Returns the realpath of @pathname on success, NULL otherwise.
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*/
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char *tomoyo_realpath_nofollow(const char *pathname)
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{
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struct path path;
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if (pathname && kern_path(pathname, 0, &path) == 0) {
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char *buf = tomoyo_realpath_from_path(&path);
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path_put(&path);
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return buf;
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}
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return NULL;
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}
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