Commit ba32744a authored May 25, 2024 by Roman Smirnov Committed by Hui Tang May 25, 2024

fbmon: prevent division by zero in fb_videomode_from_videomode()

stable inclusion
from stable-v5.10.215
commit 951838fee462aa01fa2a6a91d56f9a495082e7f0
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9QGIW
CVE: CVE-2024-35922

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=951838fee462aa01fa2a6a91d56f9a495082e7f0



---------------------------

[ 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>
Signed-off-by: Hui Tang <tanghui20@huawei.com>

parent 8d7f4806

drivers/video/fbdev/core/fbmon.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -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;