Date: Fri, 20 Jun 1997 14:59:13 +0900 (JST) From: shigio@wafu.netgate.net To: FreeBSD-gnats-submit@FreeBSD.ORG Cc: shigio@wafu.netgate.net Subject: misc/3911: realpath(3) fall into infinit loop. Message-ID: <199706192206.WAA10618@wafu.netgate.net> Resent-Message-ID: <199706200610.XAA13999@hub.freebsd.org>
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>Number: 3911
>Category: misc
>Synopsis: realpath(3) fall into infinit loop.
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Jun 19 23:10:03 PDT 1997
>Last-Modified:
>Originator: Shigio Yamaguchi
>Organization:
Freelance programmer
>Release: FreeBSD 2.2.1-RELEASE i386
>Environment:
All environment
>Description:
Realpath fall into infinit loop when encounter looped symbolic link.
It should break when over MAXSYMLINKS symbolic links are encountered
like system calls.
>How-To-Repeat:
[test.c]
-----------------------------------------------------
#include <stdio.h>
#include <sys/param.h>
#include <stdlib.h>
#include <errno.h>
main() {
char buf[MAXPATHLEN];
char *p;
printf("You can see this message.\n");
p = realpath("a", buf);
printf("You cannot see this message.\n");
if (p == NULL) {
printf("errno = %d\n", errno);
perror("realpath");
exit(1);
}
printf("%s\n", p);
exit(0);
}
-----------------------------------------------------
% cc test.c
% ln -s a b
% ln -s b a
% ./a.out
You can see this message.
... doesn't return ...
>Fix:
[/usr/src/lib/libc/stdlib/realpath.c]
*** realpath.c.org Wed May 21 22:27:22 1997
--- realpath.c Fri Jun 20 14:51:08 1997
***************
*** 62,67 ****
--- 62,68 ----
struct stat sb;
int fd, n, rootd, serrno;
char *p, *q, wbuf[MAXPATHLEN];
+ int symlinks = 0;
/* Save the starting point. */
if ((fd = open(".", O_RDONLY)) < 0) {
***************
*** 100,105 ****
--- 101,110 ----
/* 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;
+ }
n = readlink(p, resolved, MAXPATHLEN);
if (n < 0)
goto err1;
>Audit-Trail:
>Unformatted:
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