linux-kernel - Re: [PATCH v3 1/4] ozwpan: Use proper check to prevent heap overflow

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Message-ID: <20150529120042.GL28762@mwanda>
Date:	Fri, 29 May 2015 15:00:42 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Jason A. Donenfeld" <Jason@...c4.com>
Cc:	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	Shigekatsu Tateno <shigekatsu.tateno@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 1/4] ozwpan: Use proper check to prevent heap overflow

On Fri, May 29, 2015 at 01:06:58PM +0200, Jason A. Donenfeld wrote:
> --- a/drivers/staging/ozwpan/ozusbsvc1.c
> +++ b/drivers/staging/ozwpan/ozusbsvc1.c
> @@ -390,10 +390,15 @@ void oz_usb_rx(struct oz_pd *pd, struct oz_elt *elt)
>  	case OZ_GET_DESC_RSP: {
>  			struct oz_get_desc_rsp *body =
>  				(struct oz_get_desc_rsp *)usb_hdr;
> -			int data_len = elt->length -
> -					sizeof(struct oz_get_desc_rsp) + 1;
> -			u16 offs = le16_to_cpu(get_unaligned(&body->offset));
> -			u16 total_size =
> +			u16 offs, total_size;
> +			u8 data_len;
> +
> +			if (elt->length < sizeof(struct oz_get_desc_rsp) - 1)
> +				break;
> +			data_len = elt->length -
> +					(sizeof(struct oz_get_desc_rsp) - 1);

Gar...  I'm really sorry.  I wanted to Ack these and be done but why did
the + 1 change to a - 1?  And I had the same question about the other
patch as well.

Sorry for the hassle and thanks for doing this work.

regarsd,
dan carpenter


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