Re: [PATCH] pxa3xx-gcu: Fix integer overflow in pxa3xx_gcu_write

[Helge Deller <deller@gmx.de>]

Hi Hyunwoo,

On 6/11/22 21:28, Hyunwoo Kim wrote:
> In pxa3xx_gcu_write, a count parameter of
> type size_t is passed to words of type int.
> Then, copy_from_user may cause a heap overflow because
> it is used as the third argument of copy_from_user.

I suggest to simply change the type of "words" a few lines above:
Instead of
        int words = count / 4;
use
        size_t words = count / 4;

count is already of type size_t and then you don't need to check against < 0.

Can you resend such a patch?

Helge

>
> Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
> ---
>  drivers/video/fbdev/pxa3xx-gcu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/pxa3xx-gcu.c b/drivers/video/fbdev/pxa3xx-gcu.c
> index 043cc8f9ef1c..5ca6d37e365f 100644
> --- a/drivers/video/fbdev/pxa3xx-gcu.c
> +++ b/drivers/video/fbdev/pxa3xx-gcu.c
> @@ -389,7 +389,7 @@ pxa3xx_gcu_write(struct file *file, const char *buff,
>  	priv->shared->num_words += words;
>
>  	/* Last word reserved for batch buffer end command */
> -	if (words >= PXA3XX_GCU_BATCH_WORDS)
> +	if (words >= PXA3XX_GCU_BATCH_WORDS || words < 0)
>  		return -E2BIG;
>
>  	/* Wait for a free buffer */