2024-12-07 - Adventures In Bitrot, xvi Crash Fix

I have been using xvi [1] as my EDITOR on Alpine Linux.

I log in in over the serial port from my FreeDOS desktop. When my serial port speed is 9600 baud, everything works fine. When the speed is 115200 baud, xvi crashes.

    $ xvi
    Segmentation fault

GDB reveals something in xvi-2.50.3/src/unix.c at line 576.

    ospeed = cfgetospeed(&cooked_state);

When the baud rate is 115200, ospeed is set to 4098. The crash actually happens in GNU termcap, in termcap-1.3.1/termcap.c at line 336.

    speed = speeds[ospeed];

The array range is from 0 to 18. When ospeed is 4098, it is way out of bounds. I fixed this with the following local change [2].

    --- xvi-2.50.3/src/unix.c.orig
    +++ xvi-2.50.3/src/unix.c
    @@ -574,6 +574,10 @@
     #ifdef        TERMIO
     #   ifdef        POSIX
             ospeed = cfgetospeed(&cooked_state);
    +        if (ospeed > 18) {
    +                /* GNU termcap can't handle large values */
    +                ospeed = 0;
    +        }
     #   else        /* not POSIX */
             ospeed = speeds[cooked_state.c_cflag & CBAUD];
     #   endif

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