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Path: utzoo!watmath!clyde!caip!brl-adm!brl-smoke!smoke!ron@BRL.ARPA
From: ron@BRL.ARPA
Newsgroups: net.unix-wizards
Subject: brl-vgr Bug Report
Message-ID: <4573@brl-smoke.ARPA>
Date: Mon, 13-Oct-86 18:53:07 EDT
Article-I.D.: brl-smok.4573
Posted: Mon Oct 13 18:53:07 1986
Date-Received: Tue, 14-Oct-86 06:53:57 EDT
Sender: news@brl-smoke.ARPA
Lines: 127

Subject: Short summary of the problem
Index:	lib/libc/gen/getusershell.c 4.3BSD

Description:
	Setusershell and endusershell are ineffective and
	sometimes dump core.

Repeat-By:
	Do a few getusershell calls with an interspersed setusershell
	and/or endusershell.
Fix:
	The problem is that getusershell.c is horrible.  Endusershell
	may free things that have not been malloced.  There are two
	separate instances of the shells pointer one local to getusershell.
	Setusershell sets a different one than the one getusershell uses.

	A fixed up version follows:
/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)getusershell.c	5.2 (Berkeley) 3/9/86";
#endif LIBC_SCCS and not lint

#include <sys/param.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <ctype.h>
#include <stdio.h>

#define SHELLS "/etc/shells"

/*
 * Do not add local shells here.  They should be added in /etc/shells
 */
static char *okshells[] =
    { "/bin/sh", "/bin/csh", 0 };

static int inprogress;
static char **shells, *strings;
extern char **initshells();

/*
 * Get a list of shells from SHELLS, if it exists.
 */
char *
getusershell()
{
	char *ret;
	static char **shp;

	if (!inprogress)
		shp = initshells();
	ret = *shp;
	if (*shp != NULL)
		shp++;
	return (ret);
}

endusershell()
{
	
	if (shells != NULL)
		free((char *)shells);
	shells = NULL;
	if (strings != NULL)
		free(strings);
	strings = NULL;
	inprogress = 0;
}

setusershell()
{
	endusershell();
}

static char **
initshells()
{
	register char **sp, *cp;
	register FILE *fp;
	struct stat statb;
	extern char *malloc(), *calloc();

	inprogress = 1;
	if (shells != NULL)
		free((char *)shells);
	shells = NULL;
	if (strings != NULL)
		free(strings);
	strings = NULL;
	if ((fp = fopen(SHELLS, "r")) == (FILE *)0)
		return(okshells);
	if (fstat(fileno(fp), &statb) == -1) {
		(void)fclose(fp);
		return(okshells);
	}
	if ((strings = malloc((unsigned)statb.st_size)) == NULL) {
		(void)fclose(fp);
		return(okshells);
	}
	shells = (char **)calloc((unsigned)statb.st_size / 3, sizeof (char *));
	if (shells == NULL) {
		(void)fclose(fp);
		free(strings);
		strings = NULL;
		return(okshells);
	}
	sp = shells;
	cp = strings;
	while (fgets(cp, MAXPATHLEN + 1, fp) != NULL) {
		while (!isspace(*cp) != '/' && *cp != '\0')
			cp++;
		if (*cp == '#' || *cp == '\0')
			continue;
		*sp++ = cp;
		while (!isspace(*cp) && *cp != '#' && *cp != '\0')
			cp++;
		*cp++ = '\0';
	}
	*sp = (char *)0;
	(void)fclose(fp);
	return (shells);
}