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after vfork() isn't ok to calling setsid

/*************************************************************************
* (C) 2013 AITNET ltd - Sofia/Bulgaria - <misho@aitnet.org>
*  by Michael Pounov <misho@elwix.org>
*
* $Author: misho $
* $Id: pio.c,v 1.9.6.1 2024/10/26 14:42:34 misho Exp $
*
**************************************************************************
The ELWIX and AITNET software is distributed under the following
terms:

All of the documentation and software included in the ELWIX and AITNET
Releases is copyrighted by ELWIX - Sofia/Bulgaria <info@elwix.org>

Copyright 2004 - 2024
	by Michael Pounov <misho@elwix.org>.  All rights reserved.

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.
3. All advertising materials mentioning features or use of this software
   must display the following acknowledgement:
This product includes software developed by Michael Pounov <misho@elwix.org>
ELWIX - Embedded LightWeight unIX and its contributors.
4. Neither the name of AITNET 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 AITNET 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.
*/
#include "global.h"


#ifdef __linux__
#define __USE_GNU

#ifndef O_CLOEXEC
#define O_CLOEXEC	02000000
#endif
#endif

extern char **environ;

pio_pid_t pio_pidlist = SLIST_HEAD_INITIALIZER(pio_pidlist);
#ifdef HAVE_LIBPTHREAD
static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;

#define	THREAD_LOCK()	pthread_mutex_lock(&pidlist_mutex)
#define	THREAD_UNLOCK()	pthread_mutex_unlock(&pidlist_mutex)
#else
#define	THREAD_LOCK()
#define	THREAD_UNLOCK()
#endif

/*
 * e_popen() - ELWIX replacement of standard popen
 *
 * @command = command
 * @type = type
 * @ppid = return pid of child program
 * 	If value of *ppid is -1 when invoke routine then child will be session leader
 * return: NULL error or !=NULL open program
 */
#ifdef POPEN_STREAM
FILE *
#else
int
#endif
e_popen(const char *command, const char *type, pid_t *ppid)
{
	return e_popen2(command, type, ppid, NULL, 0);
}

/*
 * e_popen2() - ELWIX replacement of standard popen with post close of chosen handles
 *
 * @command = command
 * @type = type
 * @ppid = return pid of child program 
 * 	If value of *ppid is -1 when invoke routine then child will be session leader
 * @fds = file descriptor array for close when fork
 * @fdslen = fds number of descriptors
 * return: NULL error or !=NULL open program
 */
#ifdef POPEN_STREAM
FILE *
#else
int
#endif
e_popen2(const char *command, const char *type, pid_t *ppid, int *fds, size_t fdslen)
{
	struct tagPIOPID *cur, *p;
	int pdes[2], pid, twoway, cloexec, i;
	char *argv[4];

	if (!command || !type)
#ifdef POPEN_STREAM
		return NULL;
#else
		return -1;
#endif

	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])))
#ifdef POPEN_STREAM
			return NULL;
#else
			return -1;
#endif
	}
	if (socketpair(AF_UNIX, SOCK_STREAM | (cloexec ? O_CLOEXEC : 0), 
				0, pdes) < 0) {
		LOGERR;
#ifdef POPEN_STREAM
		return NULL;
#else
		return -1;
#endif
	}

	if (!(cur = e_malloc(sizeof(struct tagPIOPID)))) {
		close(pdes[0]);
		close(pdes[1]);
#ifdef POPEN_STREAM
		return NULL;
#else
		return -1;
#endif
	}

	argv[0] = "sh";
	argv[1] = "-c";
	argv[2] = (char *) command;
	argv[3] = NULL;

	THREAD_LOCK();
	switch (pid = fork()) {
	case -1:			/* Error. */
		LOGERR;
		THREAD_UNLOCK();
		close(pdes[0]);
		close(pdes[1]);
		e_free(cur);
#ifdef POPEN_STREAM
		return NULL;
#else
		return -1;
#endif
		/* NOTREACHED */
	case 0:				/* Child. */
		if (ppid && *ppid == -1)
			setsid();

		if (fds && fdslen) {
			for (i = 0; i < fdslen; i++)
				close(fds[i]);
		}

		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 (!cloexec)
				close(pdes[0]);
			if (pdes[1] != STDOUT_FILENO) {
				dup2(pdes[1], STDOUT_FILENO);
				if (!cloexec)
					close(pdes[1]);
				if (twoway)
					dup2(STDOUT_FILENO, STDIN_FILENO);
			} else if (twoway && (pdes[1] != STDIN_FILENO)) {
				dup2(pdes[1], STDIN_FILENO);
				if (cloexec)
					fcntl(pdes[1], F_SETFD, 0);
			} else if (cloexec)
				fcntl(pdes[1], F_SETFD, 0);
		} else {
			if (pdes[0] != STDIN_FILENO) {
				dup2(pdes[0], STDIN_FILENO);
				if (!cloexec)
					close(pdes[0]);
			} else if (cloexec)
				fcntl(pdes[0], F_SETFD, 0);
			if (!cloexec)
				close(pdes[1]);
		}
		SLIST_FOREACH(p, &pio_pidlist, next)
#ifdef POPEN_STREAM
			close(fileno(p->f.fp));
#else
			close(p->f.fd);
#endif
		execve(_PATH_BSHELL, argv, environ);
		_exit(127);
		/* NOTREACHED */
	default:
		if (ppid)
			*ppid = pid;
	}
	THREAD_UNLOCK();

	/* Parent; assume fdopen can't fail. */
	if (*type == 'r') {
#ifdef POPEN_STREAM
		cur->f.fp = fdopen(pdes[0], type);
#else
		cur->f.fd = pdes[0];
#endif
		close(pdes[1]);
	} else {
#ifdef POPEN_STREAM
		cur->f.fp = fdopen(pdes[1], type);
#else
		cur->f.fd = pdes[1];
#endif
		close(pdes[0]);
	}

	/* Link into list of file descriptors. */
	cur->pid = pid;
	THREAD_LOCK();
	SLIST_INSERT_HEAD(&pio_pidlist, cur, next);
	THREAD_UNLOCK();

#ifdef POPEN_STREAM
	return cur->f.fp;
#else
	return cur->f.fd;
#endif
}

/*
 * e_pclose() - ELWIX replacement of standard pclose
 *
 * @iop = popen handle
 * return: -1 error or !=-1 pid status
 */
int
#ifdef POPEN_STREAM
e_pclose(FILE *iop)
#else
e_pclose(int iop)
#endif
{
	struct tagPIOPID *cur, *last = NULL;
	int pstat = 0;
	pid_t pid;

	if (!iop)
		return -1;

	/*
	 * Find the appropriate file pointer and remove it from the list.
	 */
	THREAD_LOCK();
	SLIST_FOREACH(cur, &pio_pidlist, next) {
#ifdef POPEN_STREAM
		if (cur->f.fp == iop)
#else
		if (cur->f.fd == iop)
#endif
			break;
		last = cur;
	}
	if (!cur) {
		THREAD_UNLOCK();
		return (-1);
	}
	if (!last)
		SLIST_REMOVE_HEAD(&pio_pidlist, next);
	else
		SLIST_REMOVE_AFTER(last, next);
	THREAD_UNLOCK();

#ifdef POPEN_STREAM
	fclose(iop);
#else
	close(iop);
#endif

	do {
		pid = wait4(cur->pid, &pstat, 0, NULL);
	} while (pid == -1 && errno == EINTR);

	e_free(cur);

	return (pid == -1 ? -1 : pstat);
}

/*
 * pio_pgetpid() - Get tagPIOPID structure from file handle
 *
 * @iop = popen handle
 * return: NULL error or !=NULL tagPIOPID structure
 */
struct tagPIOPID *
#ifdef POPEN_STREAM
pio_pgetpid(FILE *iop)
#else
pio_pgetpid(int iop)
#endif
{
	struct tagPIOPID *p;

	if (!iop)
		return NULL;

	THREAD_LOCK();
	SLIST_FOREACH(p, &pio_pidlist, next)
#ifdef POPEN_STREAM
		if (p->f.fp == iop)
#else
		if (p->f.fd == iop)
#endif
			break;
	THREAD_UNLOCK();

	return p;
}

/*
 * pio_pchkpid() - Check exit status of child programs
 *
 * @pids = return tagPIOPID structures of exited programs, 
 * 		if !=NULL must call array_Destroy()
 * return: -1 error or >-1 exited programs
 */
int
pio_pchkpid(array_t ** __restrict pids)
{
	register int ret = 0;
	struct tagPIOPID *p;
	array_t *pa = NULL;

	if (pids) {
		if (!(pa = array_Init(0)))
			return -1;
		else
			*pids = pa;
	}

	THREAD_LOCK();
	SLIST_FOREACH(p, &pio_pidlist, next)
#ifdef POPEN_STREAM
		if (p->f.fp && waitpid(p->pid, &p->stat, WNOHANG) > 0) {
#else
		if (p->f.fd && waitpid(p->pid, &p->stat, WNOHANG) > 0) {
#endif
			if (pids)
				array_Push(pa, p, 0);
			ret++;
		}
	THREAD_UNLOCK();

	return ret;
}