[PATCH] 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>
---
 drivers/video/fbdev/core/fbmon.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
index 79e5bfbdd34c..bd98b138da6a 100644
--- a/drivers/video/fbdev/core/fbmon.c
+++ b/drivers/video/fbdev/core/fbmon.c
@@ -1311,7 +1311,7 @@ int fb_get_mode(int flags, u32 val, struct 
fb_var_screeninfo *var, struct fb_inf
 int fb_videomode_from_videomode(const struct videomode *vm,
                                struct fb_videomode *fbmode)
 {
-       unsigned int htotal, vtotal;
+       unsigned int htotal, vtotal, hfreq;
 
        fbmode->xres = vm->hactive;
        fbmode->left_margin = vm->hback_porch;
@@ -1345,7 +1345,8 @@ int fb_videomode_from_videomode(const struct videomode 
*vm,
                 vm->vsync_len;
        /* prevent division by zero */
        if (htotal && vtotal) {
-               fbmode->refresh = vm->pixelclock / (htotal * vtotal);
+               hfreq = vm->pixelclock / htotal;
+               fbmode->refresh = hfreq / vtotal;
        /* a mode must have htotal and vtotal != 0 or it is invalid */
        } else {
                fbmode->refresh = 0;
-- 
2.34.1