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Subject: Re: [RFCv2 bluetooth-next 14/16] ieee802154: 6lowpan: check on valid
 802.15.4 frame
References: <1440089265-23366-1-git-send-email-alex.aring@gmail.com>
 <1440089265-23366-15-git-send-email-alex.aring@gmail.com>
From: Stefan Schmidt <stefan@osg.samsung.com>
Message-ID: <55E37DA5.5030604@osg.samsung.com>
Date: Mon, 31 Aug 2015 00:03:17 +0200
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To: Alexander Aring <alex.aring@gmail.com>, linux-wpan@vger.kernel.org
Cc: kernel@pengutronix.de

Hello.

On 20/08/15 18:47, Alexander Aring wrote:
> This patch adds frame control checks to check if the received frame is
> something which could contain a 6LoWPAN packet.
>
> Signed-off-by: Alexander Aring <alex.aring@gmail.com>
> ---
>   include/linux/ieee802154.h  | 25 +++++++++++++++++++++++++
>   include/net/mac802154.h     | 15 +++++++++++++++
>   net/ieee802154/6lowpan/rx.c |  8 ++++++++
>   3 files changed, 48 insertions(+)
>
> diff --git a/include/linux/ieee802154.h b/include/linux/ieee802154.h
> index 1dc1f4e..db01492 100644
> --- a/include/linux/ieee802154.h
> +++ b/include/linux/ieee802154.h
> @@ -205,6 +205,31 @@ enum {
>   	IEEE802154_SCAN_IN_PROGRESS = 0xfc,
>   };
>   
> +/* frame control handling */
> +#define IEEE802154_FCTL_FTYPE		0x0003
> +#define IEEE802154_FCTL_INTRA_PAN	0x0040
> +
> +#define IEEE802154_FTYPE_DATA		0x0001
> +
> +/*
> + * ieee802154_is_data - check if type is IEEE802154_FTYPE_DATA
> + * @fc: frame control bytes in little-endian byteorder
> + */
> +static inline int ieee802154_is_data(__le16 fc)
> +{
> +	return (fc & cpu_to_le16(IEEE802154_FCTL_FTYPE)) ==
> +		cpu_to_le16(IEEE802154_FTYPE_DATA);
> +}
> +
> +/**
> + * ieee802154_is_intra_pan - check if intra pan id communication
> + * @fc: frame control bytes in little-endian byteorder
> + */
> +static inline bool ieee802154_is_intra_pan(__le16 fc)
> +{
> +	return fc & cpu_to_le16(IEEE802154_FCTL_INTRA_PAN);
> +}
> +
>   /**
>    * ieee802154_is_valid_psdu_len - check if psdu len is valid
>    * available lengths:
> diff --git a/include/net/mac802154.h b/include/net/mac802154.h
> index b7f9961..32bd7c0 100644
> --- a/include/net/mac802154.h
> +++ b/include/net/mac802154.h
> @@ -250,6 +250,21 @@ struct ieee802154_ops {
>   };
>   
>   /**
> + * ieee802154_get_fc_from_skb - get the frame control field from an skb
> + * @skb: skb where the frame control field will be get from
> + */
> +static inline __le16 ieee802154_get_fc_from_skb(const struct sk_buff *skb)
> +{
> +	/* return some invalid fc on failure */
> +	if (unlikely(skb->mac_len < 2)) {
> +		WARN_ON(1);
> +		return cpu_to_le16(0);
> +	}
> +
> +	return (__force __le16)__get_unaligned_memmove16(skb_mac_header(skb));
> +}
> +
> +/**
>    * ieee802154_be64_to_le64 - copies and convert be64 to le64
>    * @le64_dst: le64 destination pointer
>    * @be64_src: be64 source pointer
> diff --git a/net/ieee802154/6lowpan/rx.c b/net/ieee802154/6lowpan/rx.c
> index f98ebf5..5be996a 100644
> --- a/net/ieee802154/6lowpan/rx.c
> +++ b/net/ieee802154/6lowpan/rx.c
> @@ -11,6 +11,7 @@
>   #include <linux/if_arp.h>
>   
>   #include <net/6lowpan.h>
> +#include <net/mac802154.h>
>   #include <net/ieee802154_netdev.h>
>   
>   #include "6lowpan_i.h"
> @@ -278,6 +279,13 @@ static inline bool lowpan_is_reserved(u8 dispatch)
>    */
>   static inline bool lowpan_rx_h_check(struct sk_buff *skb)
>   {
> +	__le16 fc = ieee802154_get_fc_from_skb(skb);
> +
> +	/* check on ieee802154 conform 6LoWPAN header */
> +	if (!ieee802154_is_data(fc) ||
> +	    !ieee802154_is_intra_pan(fc))
> +		return false;
> +
>   	/* check if we can dereference the dispatch */
>   	if (unlikely(!skb->len))
>   		return false;

Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>

regards
Stefan Schmidt