Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!mips!cmic!garvey
From: garvey@cmic.UUCP (Joe Garvey)
Newsgroups: comp.sys.hp
Subject: Beware of serial port programs run by users
Keywords: breaks hpux, warning, 4-port mux, hp9000/3xx
Message-ID: <235@cmic.UUCP>
Date: 2 Feb 90 21:30:16 GMT
Organization: Califonia Microwave Inc., Sunnyvale, CA.
Lines: 97

I was doing a little program to read/write from a serial interface on my
HP 9000/370 running HP-UX 6.5. To my dismay, a small little software bug
screwed the interface to a fair-thee-well. This program can be run by any
user with access to the port. There should *not* be a getty running on this
port, and a getty running on the other ports. It does not seem to affect the
internal serial port (other than to give it a temporarily ridiculous set of
settings).

The response center considers this a feature. I consider it a bug. You decide
for yourself.

I call this program wedge.c... because of the effect it has. Consider yourself
warned. After all forwarned is forarmed (four armed might actually be better
:-) ).

-------------------------- cut here ------------------------------------------
/*
 * This little demo program will cause a 4-port mux in a series 300 computer
 * to permenantly go out to lunch. In fact, in my case I used it on port 2
 * and ports 0, 1, and 2 ceased to function. (You could see the getty issue
 * a prompt, but could not respond.) /dev/tty13.2 has no getty running on it.
 *
 * The only way out of this is to reset (turn the power off) the computer!!!
 * Any user can do this. Take heed a protect your serial ports accordingly.
 *
 * Modification History:
 * Joe Garvey, Jan 1990: Created to show HP what happened when I made a simple
 *    mistake.
 *
 */

#include <stdio.h>
#include <termio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

static int RAU_fd;                            /* file descriptor for RAU line */

main ()

{

/***** Definitions *****/

struct termio RAU_Line_Settings;


/***** Code *****/

if ((RAU_fd = open("/dev/tty13.2", O_RDWR)) < 0)
   {
   fprintf(stderr, "%s: ", "wedge");
   fprintf(stderr, "Couldn't open RAU line \"%s\"\n", "/dev/tty13.2");
   exit(1);
   }

RAU_Line_Settings.c_iflag = IGNBRK | PARMRK | INPCK | IXANY;
RAU_Line_Settings.c_oflag = ONOCR;

                     /* use of CSTOP instead of CSTOPB screws a 4-port mux up */
                     /* even the ports you're not using!!!                    */
/* right */
RAU_Line_Settings.c_cflag = B2400 | CSTOPB | CREAD | CS8 | PARENB | PARODD
                                                                        | HUPCL;
*/
/* wrong */
RAU_Line_Settings.c_cflag = B2400 | CSTOP | CREAD | CS8 | PARENB | PARODD
                                                                        | HUPCL;
RAU_Line_Settings.c_lflag = 0;
RAU_Line_Settings.c_line = 0;
RAU_Line_Settings.c_cc[VTIME] = 1;
RAU_Line_Settings.c_cc[VMIN] = 0;

if (ioctl(RAU_fd, TCSETA, &RAU_Line_Settings) < 0)
   {
   fprintf(stderr, "%s: ", "wedge");
   fprintf(stderr, "Couldn't configure RAU line\n");
   exit(1);
   }

sleep(1000);        /* use this delay to check settings of line using stty(1) */
                    /* stty -a < /dev/tty13.2                                 */

return;

}

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Joe Garvey                       UUCP: {apple,backbone}!versatc!mips!cmic!garvey
California Microwave             Internet: garvey%cmic@mips.com
990 Almanor Ave                  HP Desk: xxx ("mips!cmic!garvey")/hp1900/ux
Sunnyvale, Ca, 94086             800-831-3104 (outside CA)
408-720-6439 (let it ring)       800-824-7814 (inside CA)