gww@marduk.UUCP (Gary Winiger) (09/05/87)
Subject: Timezone fields can be destroyed +Fix
Index: libc/gen/timezone.c 4.3BSD +Fix
Description:
Certain calls to timezone(3) will return a pointer not to
an area of bss, but to the static data that timezone uses
to determine the correct timezone nmumonic.
On systems which permit the modification of static data, this
may result in future calls to timezone to return bad information.
On systems in which static data is in a write protected segment,
segmentation violations may occur.
Repeat-By:
Have no TIMEZONE environment variable.
extern char *timezone();
main()
{
char *tz;
tz = timezone(8*60,1);
printf("The current timezone is %s\n", tz);
strcpy(tz, "ZZZ");
tz = timezone(8*60,1);
printf("The future timezone is %s\n", tz);
}
On a system which permits modification of static data, this will
print out a future time zone of ZZZ.
On a system in which static data is in a write protected segment,
it will cause a segmentation fault.
Fix:
Always return the timezone in the bss area.
The attached code solves this problem at Elxsi.
Gary..
{ucbvax!sun,lll-lcc!lll-tis,amdahl!altos86,bridge2}!elxsi!gww
--------- cut --------- snip --------- :.,$w diff -------------
*** /tmp/,RCSt1000316 Wed Jul 8 18:55:00 1987
--- timezone.c Wed Jul 8 18:54:23 1987
***************
*** 1,5 ****
--- 1,10 ----
/*
* $Log: timezone.c,v $
+ * Revision 1.2 87/07/08 18:53:25 gww
+ * Don't return a pointer to static data, but copy the data to the
+ * bss area. Then if the user overwrites it, the data will still be
+ * valid for the next call.
+ *
* Revision 1.1 87/01/15 15:35:59 gww
* Initial revision
*
***************
*** 11,17 ****
*/
#if defined(LIBC_SCCS) && !defined(lint)
! static char *ERcsId = "$Header: timezone.c,v 1.1 87/01/15 15:35:59 gww Exp $ ENIX BSD";
static char sccsid[] = "@(#)timezone.c 5.2 (Berkeley) 3/9/86";
#endif LIBC_SCCS and not lint
--- 16,22 ----
*/
#if defined(LIBC_SCCS) && !defined(lint)
! static char *ERcsId = "$Header: timezone.c,v 1.2 87/07/08 18:53:25 gww Exp $ ENIX BSD";
static char sccsid[] = "@(#)timezone.c 5.2 (Berkeley) 3/9/86";
#endif LIBC_SCCS and not lint
***************
*** 72,80 ****
for (zp=zonetab; zp->offset!=-1; zp++)
if (zp->offset==zone) {
if (dst && zp->dlzone)
! return(zp->dlzone);
if (!dst && zp->stdzone)
! return(zp->stdzone);
}
if (zone<0) {
zone = -zone;
--- 77,86 ----
for (zp=zonetab; zp->offset!=-1; zp++)
if (zp->offset==zone) {
if (dst && zp->dlzone)
! strcpy(czone, zp->dlzone);
if (!dst && zp->stdzone)
! strcpy(czone, zp->stdzone);
! return (czone);
}
if (zone<0) {
zone = -zone;