linux-kernel - Re: [PATCH] tty: an overflow of multiplication in drivers/tty/cyclades.c

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Date:	Tue, 17 Dec 2013 09:39:34 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	xqx12 <s2exqx@...il.com>
Cc:	jslaby@...e.cz, linux-kernel@...r.kernel.org, chyyuu@...il.com,
	xuyongjiande@...il.com, xqx12 <xiaoqixue_1@....com>
Subject: Re: [PATCH] tty: an overflow of multiplication in
 drivers/tty/cyclades.c

On Mon, Dec 16, 2013 at 10:21:36PM +0800, xqx12 wrote:
> there is an overflow in the code :
> cyz_polling_cycle = (arg * HZ) / 1000,
> the multiplicator arg comes from user, so it may be an overflow if
> arg is a big number. And the value of cyc_polling_cycle will be
> wrong when it is used next time.
> 
> Reported-by: Qixue Xiao <xiaoqixue_1@....com>
> Suggested-by: Yongjian Xu <xuyongjiande@...il.com>
> Suggested-by: Yu Chen <chyyuu@...il.com>
> Signed-off-by: Qixue Xiao <xiaoqixue_1@....com>
> ---
>  drivers/tty/cyclades.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
> index cfeec97..7eec1c5 100644
> --- a/drivers/tty/cyclades.c
> +++ b/drivers/tty/cyclades.c
> @@ -2728,7 +2728,8 @@ cy_ioctl(struct tty_struct *tty,
>  		break;
>  #ifndef CONFIG_CYZ_INTR
>  	case CYZSETPOLLCYCLE:
> +		if (arg > LONG_MAX / HZ)
> +			return -ENODEV;

This patch fails to apply at all to any of my trees, can you please redo
it against the latest tty tree and resend it so that I can apply it?

thanks,

greg k-h
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