[PATCH AUTOSEL 6.1 15/15] fbmon: prevent division by zero in fb_videomode_from_videomode()

Sasha Levin
2024-04-03T17:19:39Z

From: Roman Smirnov <r.smirnov@omp.ru>

[ Upstream commit c2d953276b8b27459baed1277a4fdd5dd9bd4126 ]

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.smirnov@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/video/fbdev/core/fbmon.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
index b0e690f41025a..9ca99da3a56a0 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, total;

fbmode->xres = vm->hactive;
fbmode->left_margin = vm->hback_porch;
@@ -1344,8 +1344,9 @@ 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) {
- fbmode->refresh = vm->pixelclock / (htotal * vtotal);
+ total = htotal * vtotal;
+ if (total) {
+ fbmode->refresh = vm->pixelclock / total;
/* a mode must have htotal and vtotal != 0 or it is invalid */
} else {
fbmode->refresh = 0;
--
2.43.0