queue-6.1/fbmon-prevent-division-by-zero-in-fb_videomode_from_.patch

   1 From fe6a7d6bdb5004c5b5e57e94be16d60769df9473 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Tue, 19 Mar 2024 11:13:44 +0300
   4 Subject: fbmon: prevent division by zero in fb_videomode_from_videomode()
   5
   6 From: Roman Smirnov <r.smirnov@omp.ru>
   7
   8 [ Upstream commit c2d953276b8b27459baed1277a4fdd5dd9bd4126 ]
   9
  10 The expression htotal * vtotal can have a zero value on
  11 overflow. It is necessary to prevent division by zero like in
  12 fb_var_to_videomode().
  13
  14 Found by Linux Verification Center (linuxtesting.org) with Svace.
  15
  16 Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
  17 Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
  18 Signed-off-by: Helge Deller <deller@gmx.de>
  19 Signed-off-by: Sasha Levin <sashal@kernel.org>
  20 ---
  21  drivers/video/fbdev/core/fbmon.c | 7 ++++---
  22  1 file changed, 4 insertions(+), 3 deletions(-)
  23
  24 diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
  25 index b0e690f41025a..9ca99da3a56a0 100644
  26 --- a/drivers/video/fbdev/core/fbmon.c
  27 +++ b/drivers/video/fbdev/core/fbmon.c
  28 @@ -1311,7 +1311,7 @@ int fb_get_mode(int flags, u32 val, struct fb_var_screeninfo *var, struct fb_inf
  29  int fb_videomode_from_videomode(const struct videomode *vm,
  30                                 struct fb_videomode *fbmode)
  31  {
  32 -       unsigned int htotal, vtotal;
  33 +       unsigned int htotal, vtotal, total;
  34
  35         fbmode->xres = vm->hactive;
  36         fbmode->left_margin = vm->hback_porch;
  37 @@ -1344,8 +1344,9 @@ int fb_videomode_from_videomode(const struct videomode *vm,
  38         vtotal = vm->vactive + vm->vfront_porch + vm->vback_porch +
  39                  vm->vsync_len;
  40         /* prevent division by zero */
  41 -       if (htotal && vtotal) {
  42 -               fbmode->refresh = vm->pixelclock / (htotal * vtotal);
  43 +       total = htotal * vtotal;
  44 +       if (total) {
  45 +               fbmode->refresh = vm->pixelclock / total;
  46         /* a mode must have htotal and vtotal != 0 or it is invalid */
  47         } else {
  48                 fbmode->refresh = 0;
  49 --
  50 2.43.0
  51