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Make realpath() thread-safe. New implementation does not use chdir(2) at all.

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Submitted by:	Constantin S. Svintsoff <kostik (at) iclub.nsu.ru>
This commit is contained in:
Max Khon 2003-03-27 20:48:53 +00:00
parent 5e2e6a67c4
commit 226a0f0f8b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=112726
2 changed files with 127 additions and 110 deletions
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4
lib/libc/stdlib/realpath.3
View File

@ -99,11 +99,7 @@ The function
may fail and set the external variable
.Va errno
for any of the errors specified for the library functions
.Xr chdir 2 ,
.Xr close 2 ,
.Xr fchdir 2 ,
.Xr lstat 2 ,
.Xr open 2 ,
.Xr readlink 2
and
.Xr getcwd 3 .

233
lib/libc/stdlib/realpath.c
View File

@ -1,9 +1,5 @@
/*
* Copyright (c) 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jan-Simon Pendry.
* Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@ -13,18 +9,14 @@
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* 3. The names of the authors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
@ -45,8 +37,6 @@ __FBSDID("$FreeBSD$");
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "un-namespace.h"
@ -59,108 +49,139 @@ __FBSDID("$FreeBSD$");
* in which case the path which caused trouble is left in (resolved).
*/
char *
realpath(path, resolved)
const char *path;
char *resolved;
realpath(const char *path, char resolved_path[MAXPATHLEN])
{
struct stat sb;
int fd, n, rootd, serrno;
char *p, *q, wbuf[PATH_MAX];
int symlinks = 0;
unsigned num_symlinks = 0;
int saved_errno = errno;
/* Save the starting point. */
if ((fd = _open(".", O_RDONLY)) < 0) {
(void)strcpy(resolved, ".");
return (NULL);
char left[MAXPATHLEN];
size_t left_len, resolved_len;
if (path[0] == '/') {
resolved_path[0] = '/';
resolved_path[1] = '\0';
if (path[1] == '\0')
return resolved_path;
resolved_len = 1;
left_len = strlcpy(left, path + 1, MAXPATHLEN);
} else {
if (getcwd(resolved_path, MAXPATHLEN) == NULL) {
strlcpy(resolved_path, ".", MAXPATHLEN);
return NULL;
}
resolved_len = strlen(resolved_path);
left_len = strlcpy(left, path, MAXPATHLEN);
}
if (left_len >= MAXPATHLEN || resolved_len >= MAXPATHLEN) {
errno = ENAMETOOLONG;
return NULL;
}
/*
* Find the dirname and basename from the path to be resolved.
* Change directory to the dirname component.
* lstat the basename part.
* if it is a symlink, read in the value and loop.
* if it is a directory, then change to that directory.
* get the current directory name and append the basename.
*/
(void)strlcpy(resolved, path, PATH_MAX);
loop:
q = strrchr(resolved, '/');
if (q != NULL) {
p = q + 1;
if (q == resolved)
q = "/";
else {
do {
--q;
} while (q > resolved && *q == '/');
q[1] = '\0';
q = resolved;
}
if (chdir(q) < 0)
goto err1;
} else
p = resolved;
while (left_len > 0) {
struct stat st;
char next_token[MAXPATHLEN];
char *p;
char *s = (p = strchr(left, '/')) ? p : left + left_len;
/* Deal with the last component. */
if (*p != '\0' && lstat(p, &sb) == 0) {
if (S_ISLNK(sb.st_mode)) {
if (++symlinks > MAXSYMLINKS) {
errno = ELOOP;
goto err1;
memmove(next_token, left, s - left);
left_len -= s - left;
if (p != NULL)
memmove(left, s + 1, left_len + 1);
next_token[s - left] = '\0';
if (resolved_path[resolved_len - 1] != '/') {
if (resolved_len + 1 >= MAXPATHLEN) {
errno = ENAMETOOLONG;
return NULL;
}
n = readlink(p, resolved, PATH_MAX - 1);
if (n < 0)
goto err1;
resolved[n] = '\0';
goto loop;
resolved_path[resolved_len++] = '/';
resolved_path[resolved_len] = '\0';
}
if (S_ISDIR(sb.st_mode)) {
if (chdir(p) < 0)
goto err1;
p = "";
if (next_token[0] == '\0')
continue;
else if (!strcmp(next_token, "."))
continue;
else if (!strcmp(next_token, "..")) {
if (resolved_len > 1) {
char *q;
/* trailing slash */
resolved_path[resolved_len - 1] = '\0';
q = strrchr(resolved_path, '/');
*q = '\0';
resolved_len = q - resolved_path;
}
continue;
}
}
/*
* Save the last component name and get the full pathname of
* the current directory.
*/
(void)strcpy(wbuf, p);
if (getcwd(resolved, PATH_MAX) == 0)
goto err1;
/*
* Join the two strings together, ensuring that the right thing
* happens if the last component is empty, or the dirname is root.
*/
if (resolved[0] == '/' && resolved[1] == '\0')
rootd = 1;
else
rootd = 0;
if (*wbuf) {
if (strlen(resolved) + strlen(wbuf) + rootd + 1 > PATH_MAX) {
/* filename */
resolved_len = strlcat(resolved_path, next_token, MAXPATHLEN);
if (resolved_len >= MAXPATHLEN) {
errno = ENAMETOOLONG;
goto err1;
return NULL;
}
if (lstat(resolved_path, &st) < 0) {
if (errno == ENOENT && p == NULL) {
errno = saved_errno;
return resolved_path;
}
return NULL;
}
if ((st.st_mode & S_IFLNK) == S_IFLNK) {
char symlink[MAXPATHLEN];
int slen;
if (num_symlinks++ > MAXSYMLINKS) {
errno = ELOOP;
return NULL;
}
slen = readlink(resolved_path, symlink, MAXPATHLEN);
if (slen < 0)
return NULL;
symlink[slen] = '\0';
if (symlink[0] == '/') {
/* absolute link */
resolved_path[1] = 0;
resolved_len = 1;
} else if (resolved_len > 1) {
char *q;
/* trailing slash */
resolved_path[resolved_len - 1] = '\0';
q = strrchr(resolved_path, '/');
*q = '\0';
resolved_len = q - resolved_path;
}
if (symlink[slen - 1] != '/' && p != NULL) {
if (slen >= MAXPATHLEN) {
errno = ENAMETOOLONG;
return NULL;
}
symlink[slen] = '/';
symlink[slen + 1] = 0;
}
if (p != NULL)
left_len = strlcat(symlink, left, MAXPATHLEN);
if (left_len > MAXPATHLEN) {
errno = ENAMETOOLONG;
return NULL;
}
left_len = strlcpy(left, symlink, MAXPATHLEN);
}
if (rootd == 0)
(void)strcat(resolved, "/");
(void)strcat(resolved, wbuf);
}
/* Go back to where we came from. */
if (fchdir(fd) < 0) {
serrno = errno;
goto err2;
}
if (resolved_len > 1 && resolved_path[resolved_len - 1] == '/')
resolved_path[resolved_len - 1] = '\0';
/* It's okay if the close fails, what's an fd more or less? */
(void)_close(fd);
return (resolved);
err1: serrno = errno;
(void)fchdir(fd);
err2: (void)_close(fd);
errno = serrno;
return (NULL);
return resolved_path;
}