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Commit 1fb52bc1 authored by Roman Smirnov's avatar Roman Smirnov Committed by Greg Kroah-Hartman
Browse files

fbmon: prevent division by zero in fb_videomode_from_videomode() 



[ 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: default avatarRoman Smirnov <r.smirnov@omp.ru>
Reviewed-by: default avatarSergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 3affd4cc

drivers/video/fbdev/core/fbmon.c

+4 −3
Original line number Diff line number Diff line
@@ -1309,7 +1309,7 @@ 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;
@@ -1342,8 +1342,9 @@ 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;