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List: linux-kernel
Subject: Re: [PATCH v3] fbmon: prevent division by zero in fb_videomode_from_videomode()
From: Helge Deller <deller () gmx ! de>
Date: 2024-03-19 12:22:57
Message-ID: 99a52bd5-7291-4ef6-a2b1-0fcb646dcff8 () gmx ! de
[Download RAW message or body]
On 3/19/24 09:13, Roman Smirnov wrote:
> 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>
> ---
> 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);
I modified your patch like this:
..
- if (htotal && vtotal) {
- fbmode->refresh = vm->pixelclock / (htotal * vtotal);
+ total = htotal * vtotal;
+ if (total) {
+ fbmode->refresh = vm->pixelclock / total;
and added it to the fbdev git tree.
https://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev.git/commit/?h=for-next
Thanks,
Helge
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