Hi Dan,
On Wed, Oct 4, 2017 at 2:50 PM, Dan Carpenter <dan.carpen...@oracle.com> wrote:
> This bug predates git but it looks like it might be simple to fix if the
> right person looked at the code.
>
> drivers/video/fbdev/controlfb.c:560 control_setup()
> error: buffer overflow 'control_mac_modes' 20 <= 21
>
> drivers/video/fbdev/controlfb.c
> 549 static void __init control_setup(char *options)
> 550 {
> 551 char *this_opt;
> 552
> 553 if (!options || !*options)
> 554 return;
> 555
> 556 while ((this_opt = strsep(&options, ",")) != NULL) {
> 557 if (!strncmp(this_opt, "vmode:", 6)) {
> 558 int vmode = simple_strtoul(this_opt+6, NULL,
> 0);
> ^^^^^
> We get vmode from the command line.
>
> 559 if (vmode > 0 && vmode <= VMODE_MAX &&
> ^^^^^^^^^
> We check that it's <= 22.
>
> 560 control_mac_modes[vmode - 1].m[1] >= 0)
> ^^^^^^^^^^^^^^^^^
> But the problem is that control_mac_modes[] only has 20 elements so the
> highest valid index is 19. vmode - 1 can be up to 21.
Nice catch!
The bug was introduced in v2.4.5.6, when 2 new modes were added to
macmodes.h, but control_mac_modes[] wasn't updated:
https://kernel.opensuse.org/cgit/kernel/diff/include/video/macmodes.h?h=v2.5.2&id=29f279c764808560eaceb88fef36cbc35c529aad
A simple fix is to check against ARRAY_SIZE(control_mac_modes) instead.
A better fix is to add the missing entries to control_mac_modes[], cfr. the
(gmail-whitespace-damaged) patch below:
--- a/drivers/video/fbdev/controlfb.h
+++ b/drivers/video/fbdev/controlfb.h
@@ -141,5 +141,7 @@ static struct max_cmodes control_mac_modes[] = {
{{ 1, 2}}, /* 1152x870, 75Hz */
{{ 0, 1}}, /* 1280x960, 75Hz */
{{ 0, 1}}, /* 1280x1024, 75Hz */
+ {{ 1, 2}}, /* 1152x768, 60Hz */
+ {{ 0, 1}}, /* 1600x1024, 60Hz */
};
(this array lists the maximum color mode (8, 16, or 32 bpp) for each
video mode given RAM restrictions (2 or 4 MiB)).
The 1152x768 mode is probably OK. Given the 1600x1024 mode has a lower
dotclock (112 MHz) than the supported 1280x960 mode, it's probably OK, too.
platinum_reg_init[] and valkyrie_reg_init[] seem to be handled fine.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
