[PATCH v3] fbmon: prevent division by zero in fb_videomode_from_videomode()

[Roman Smirnov]

The expression htotal * vtotal can have a zero value on
overflow. It is necessary to prevent division by zero like in
fb_var_to_videomode().

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smir...@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtyl...@omp.ru>
---
 V1 -> V2: Replaced the code of the first version with a check.
 V2 -> V3: Replaced the code of the second version with a zero check

 drivers/video/fbdev/core/fbmon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
index 79e5bfbdd34c..ca946919d962 100644
--- a/drivers/video/fbdev/core/fbmon.c
+++ b/drivers/video/fbdev/core/fbmon.c
@@ -1344,7 +1344,7 @@ int fb_videomode_from_videomode(const struct videomode 
*vm,
        vtotal = vm->vactive + vm->vfront_porch + vm->vback_porch +
                 vm->vsync_len;
        /* prevent division by zero */
-       if (htotal && vtotal) {
+       if (htotal && vtotal && (htotal * vtotal)) {
                fbmode->refresh = vm->pixelclock / (htotal * vtotal);
        /* a mode must have htotal and vtotal != 0 or it is invalid */
        } else {
-- 
2.34.1