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freebsd/lib/libc/gen/popen.c
Jilles Tjoelker 02804449a2 popen(): Try to prevent inappropriate fd passing even if 'e' is not used.
Even though not all race conditions can be fixed if the 'e' option is not
used, still fix some race conditions using pipe2():

* Prevent both ends of the pipe from leaking to a concurrent popen().

* Prevent the child process's end of the pipe from leaking to any concurrent
  fork and exec.

This change also simplifies the code.
2013-10-20 20:50:17 +00:00

218 lines
5.7 KiB
C

/*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software written by Ken Arnold and
* published in UNIX Review, Vol. 6, No. 8.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 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.
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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
* 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)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)popen.c 8.3 (Berkeley) 5/3/95";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "namespace.h"
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <paths.h>
#include <pthread.h>
#include "un-namespace.h"
#include "libc_private.h"
extern char **environ;
struct pid {
SLIST_ENTRY(pid) next;
FILE *fp;
pid_t pid;
};
static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;
#define THREAD_LOCK() if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
#define THREAD_UNLOCK() if (__isthreaded) _pthread_mutex_unlock(&pidlist_mutex)
FILE *
popen(command, type)
const char *command, *type;
{
struct pid *cur;
FILE *iop;
int pdes[2], pid, twoway, cloexec;
char *argv[4];
struct pid *p;
cloexec = strchr(type, 'e') != NULL;
/*
* Lite2 introduced two-way popen() pipes using _socketpair().
* FreeBSD's pipe() is bidirectional, so we use that.
*/
if (strchr(type, '+')) {
twoway = 1;
type = "r+";
} else {
twoway = 0;
if ((*type != 'r' && *type != 'w') ||
(type[1] && (type[1] != 'e' || type[2])))
return (NULL);
}
if (pipe2(pdes, O_CLOEXEC) < 0)
return (NULL);
if ((cur = malloc(sizeof(struct pid))) == NULL) {
(void)_close(pdes[0]);
(void)_close(pdes[1]);
return (NULL);
}
argv[0] = "sh";
argv[1] = "-c";
argv[2] = (char *)command;
argv[3] = NULL;
THREAD_LOCK();
switch (pid = vfork()) {
case -1: /* Error. */
THREAD_UNLOCK();
(void)_close(pdes[0]);
(void)_close(pdes[1]);
free(cur);
return (NULL);
/* NOTREACHED */
case 0: /* Child. */
if (*type == 'r') {
/*
* The _dup2() to STDIN_FILENO is repeated to avoid
* writing to pdes[1], which might corrupt the
* parent's copy. This isn't good enough in
* general, since the _exit() is no return, so
* the compiler is free to corrupt all the local
* variables.
*/
if (pdes[1] != STDOUT_FILENO) {
(void)_dup2(pdes[1], STDOUT_FILENO);
if (twoway)
(void)_dup2(STDOUT_FILENO, STDIN_FILENO);
} else if (twoway && (pdes[1] != STDIN_FILENO)) {
(void)_dup2(pdes[1], STDIN_FILENO);
(void)_fcntl(pdes[1], F_SETFD, 0);
} else
(void)_fcntl(pdes[1], F_SETFD, 0);
} else {
if (pdes[0] != STDIN_FILENO) {
(void)_dup2(pdes[0], STDIN_FILENO);
} else
(void)_fcntl(pdes[0], F_SETFD, 0);
}
SLIST_FOREACH(p, &pidlist, next)
(void)_close(fileno(p->fp));
_execve(_PATH_BSHELL, argv, environ);
_exit(127);
/* NOTREACHED */
}
THREAD_UNLOCK();
/* Parent; assume fdopen can't fail. */
if (*type == 'r') {
iop = fdopen(pdes[0], type);
(void)_close(pdes[1]);
} else {
iop = fdopen(pdes[1], type);
(void)_close(pdes[0]);
}
/* Link into list of file descriptors. */
cur->fp = iop;
cur->pid = pid;
THREAD_LOCK();
SLIST_INSERT_HEAD(&pidlist, cur, next);
THREAD_UNLOCK();
/*
* To guard against undesired fd passing with concurrent calls,
* only clear the close-on-exec flag after linking the file into
* the list which will cause an explicit close.
*/
if (!cloexec)
(void)_fcntl(*type == 'r' ? pdes[0] : pdes[1], F_SETFD, 0);
return (iop);
}
/*
* pclose --
* Pclose returns -1 if stream is not associated with a `popened' command,
* if already `pclosed', or waitpid returns an error.
*/
int
pclose(iop)
FILE *iop;
{
struct pid *cur, *last = NULL;
int pstat;
pid_t pid;
/*
* Find the appropriate file pointer and remove it from the list.
*/
THREAD_LOCK();
SLIST_FOREACH(cur, &pidlist, next) {
if (cur->fp == iop)
break;
last = cur;
}
if (cur == NULL) {
THREAD_UNLOCK();
return (-1);
}
if (last == NULL)
SLIST_REMOVE_HEAD(&pidlist, next);
else
SLIST_REMOVE_AFTER(last, next);
THREAD_UNLOCK();
(void)fclose(iop);
do {
pid = _wait4(cur->pid, &pstat, 0, (struct rusage *)0);
} while (pid == -1 && errno == EINTR);
free(cur);
return (pid == -1 ? -1 : pstat);
}