On Wed, Oct 28, 2026 at 12:14:29PM +0100, Matthieu Herrb wrote:
> On Wed, Oct 28, 2026 at 10:22:00AM +0100, Dirk-Wilhelm Peters wrote:
> > I have just found out by accident that xlock leaves its door slightly
> > ajar when using the marquee mode with a custom message:
> >
> > xlock -mode marquee -message "hack me"
> >
> > Simply type a few random characters to get back in.
> >
> > Abort trap
> >
> > This worked on several amd64 machines running 8.0 and 8.0-current.
> >
>
> This is a undefined behaviour of memcpy() on overlapping buffers. This
> patch should fix it.
>
> None of the non default modes of xlock have been seriously audited for
> bugs like that. We still recommend to stick to -mode blank (the
> default).
>
> Index: modes/marquee.c
> ===================================================================
> RCS file: /local/cvs/xenocara/app/xlockmore/modes/marquee.c,v
> diff -u -p -u -r1.1.1.1 marquee.c
> --- modes/marquee.c 26 Nov 2006 11:08:32 -0000 1.1.1.1
> +++ modes/marquee.c 28 Oct 2026 11:12:10 -0000
> @@ -269,7 +269,7 @@ add_blanks(marqueestruct * mp)
> mp->x -= 2 * char_width[(int) (' ')];
> if (mp->x <= -char_width[(int) (unsigned char) mp->modwords[0]]) {
> mp->x += char_width[(int) (unsigned char) mp->modwords[0]];
> - (void) memcpy(mp->modwords, &(mp->modwords[1]), mp->nonblanks);
> + (void) memmove(mp->modwords, &(mp->modwords[1]), mp->nonblanks);
> mp->nonblanks--;
> }
> return (mp->nonblanks < 0);
> @@ -287,7 +287,7 @@ add_letter(marqueestruct * mp, char lett
> mp->x -= char_width[(int) letter];
> if (mp->x <= -char_width[(int) (unsigned char) mp->modwords[0]]) {
> mp->x += char_width[(int) (unsigned char) mp->modwords[0]];
> - (void) memcpy(mp->modwords, &(mp->modwords[1]), mp->t);
> + (void) memmove(mp->modwords, &(mp->modwords[1]), mp->t);
> mp->modwords[mp->t] = ' ';
> mp->t--;
> } else
>
OK claudio@ on that diff. This certainly needs memmove.
--
:wq Claudio
