mac80211 : fix unaligned rx skb

mac80211 : fix unaligned rx skb

[matthieu castet]

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mac80211 is checking is the skb is aligned on 32 bit boundary.
But it is checking against ethernet header, whereas Linux expect IP
header aligned.
And ethernet ether size is 6*2+2=14, so aligning ethernet header make IP header unaligned.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 9776f73..0845fb3 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 		 * mac80211. That also explains the __skb_push()
 		 * below.
 		 */
-		align = (unsigned long)skb->data & 3;
+		align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) & 3;
 		if (align) {
 			if (WARN_ON(skb_headroom(skb) < 3)) {
 				dev_kfree_skb(skb);

Re: mac80211 : fix unaligned rx skb

[Luis R. Rodriguez]

On Thu, Jun 4, 2009 at 1:16 PM, matthieu castet <castet.matthieu@free.fr> wrote:
>

This is all I see, can you resend with patch inline?

  Luis

Re: mac80211 : fix unaligned rx skb

[Georgy Berdyshev]

Hi,

that's the inline version:
-------
mac80211 is checking is the skb is aligned on 32 bit boundary.
But it is checking against ethernet header, whereas Linux expect IP
header aligned.
And ethernet ether size is 6*2+2=14, so aligning ethernet header make
IP header unaligned.

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 9776f73..0845fb3 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 		 * mac80211. That also explains the __skb_push()
 		 * below.
 		 */
-		align = (unsigned long)skb->data & 3;
+		align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) & 3;
 		if (align) {
 			if (WARN_ON(skb_headroom(skb) < 3)) {
 				dev_kfree_skb(skb);
------------

On Thu, Jun 4, 2009 at 5:53 PM, Luis R. Rodriguez <mcgrof@gmail.com> wrote:
> On Thu, Jun 4, 2009 at 1:16 PM, matthieu castet <castet.matthieu@free.fr> wrote:
>>
>
> This is all I see, can you resend with patch inline?
>
>  Luis
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-- 
Georgy Berdyshev

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Re: mac80211 : fix unaligned rx skb

[Michael Buesch]

On Thursday 04 June 2009 23:16:13 Georgy Berdyshev wrote:
> Hi,
> 
> that's the inline version:
> -------
> mac80211 is checking is the skb is aligned on 32 bit boundary.
> But it is checking against ethernet header, whereas Linux expect IP
> header aligned.
> And ethernet ether size is 6*2+2=14, so aligning ethernet header make
> IP header unaligned.
> 
> Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
> index 9776f73..0845fb3 100644
> --- a/net/mac80211/rx.c
> +++ b/net/mac80211/rx.c
> @@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
>  		 * mac80211. That also explains the __skb_push()
>  		 * below.
>  		 */
> -		align = (unsigned long)skb->data & 3;
> +		align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) & 3;
>  		if (align) {
>  			if (WARN_ON(skb_headroom(skb) < 3)) {
>  				dev_kfree_skb(skb);

Uhm, can you give a more verbose explanation? Without that I'd say this patch is plain wrong.
What the hell does struct ethhdr have to do with wireless?
This is not ethernet. It's 802.11. There is no such thing as an ethernet header in a 802.11 packet.

-- 
Greetings, Michael.

Re: mac80211 : fix unaligned rx skb

[matthieu castet]

Michael Buesch wrote:
> On Thursday 04 June 2009 23:16:13 Georgy Berdyshev wrote:
>> Hi,
>>
>> that's the inline version:
>> -------
>> mac80211 is checking is the skb is aligned on 32 bit boundary.
>> But it is checking against ethernet header, whereas Linux expect IP
>> header aligned.
>> And ethernet ether size is 6*2+2=14, so aligning ethernet header make
>> IP header unaligned.
>>
>> Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
>> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
>> index 9776f73..0845fb3 100644
>> --- a/net/mac80211/rx.c
>> +++ b/net/mac80211/rx.c
>> @@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
>>  		 * mac80211. That also explains the __skb_push()
>>  		 * below.
>>  		 */
>> -		align = (unsigned long)skb->data & 3;
>> +		align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) & 3;
>>  		if (align) {
>>  			if (WARN_ON(skb_headroom(skb) < 3)) {
>>  				dev_kfree_skb(skb);
> 
> Uhm, can you give a more verbose explanation? Without that I'd say this patch is plain wrong.
> What the hell does struct ethhdr have to do with wireless?
 > This is not ethernet. It's 802.11. There is no such thing as an
 > ethernet header in a 802.11 packet.
 >
Where are in ieee80211_deliver_skb that is called after 
ieee80211_data_to_8023. So it is not 802.11.

Matthieu

Re: mac80211 : fix unaligned rx skb

[matthieu castet]

matthieu castet wrote:
> Michael Buesch wrote:
>> On Thursday 04 June 2009 23:16:13 Georgy Berdyshev wrote:
>>> Hi,
>>>
>>> that's the inline version:
>>> -------
>>> mac80211 is checking is the skb is aligned on 32 bit boundary.
>>> But it is checking against ethernet header, whereas Linux expect IP
>>> header aligned.
>>> And ethernet ether size is 6*2+2=14, so aligning ethernet header make
>>> IP header unaligned.
>>>
>>> Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
>>> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
>>> index 9776f73..0845fb3 100644
>>> --- a/net/mac80211/rx.c
>>> +++ b/net/mac80211/rx.c
>>> @@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data 
>>> *rx)
>>>           * mac80211. That also explains the __skb_push()
>>>           * below.
>>>           */
>>> -        align = (unsigned long)skb->data & 3;
>>> +        align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) 
>>> & 3;
>>>          if (align) {
>>>              if (WARN_ON(skb_headroom(skb) < 3)) {
>>>                  dev_kfree_skb(skb);
>>
>> Uhm, can you give a more verbose explanation? Without that I'd say 
>> this patch is plain wrong.
>> What the hell does struct ethhdr have to do with wireless?
>  > This is not ethernet. It's 802.11. There is no such thing as an
>  > ethernet header in a 802.11 packet.
>  >
> Where are in ieee80211_deliver_skb that is called after 
> ieee80211_data_to_8023. So it is not 802.11.
> 
Do you want more explanation ?

Matthieu

Re: mac80211 : fix unaligned rx skb

[Michael Buesch]

On Sunday 07 June 2009 11:24:48 matthieu castet wrote:
> matthieu castet wrote:
> > Michael Buesch wrote:
> >> On Thursday 04 June 2009 23:16:13 Georgy Berdyshev wrote:
> >>> Hi,
> >>>
> >>> that's the inline version:
> >>> -------
> >>> mac80211 is checking is the skb is aligned on 32 bit boundary.
> >>> But it is checking against ethernet header, whereas Linux expect IP
> >>> header aligned.
> >>> And ethernet ether size is 6*2+2=14, so aligning ethernet header make
> >>> IP header unaligned.
> >>>
> >>> Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
> >>> diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
> >>> index 9776f73..0845fb3 100644
> >>> --- a/net/mac80211/rx.c
> >>> +++ b/net/mac80211/rx.c
> >>> @@ -1397,7 +1397,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data 
> >>> *rx)
> >>>           * mac80211. That also explains the __skb_push()
> >>>           * below.
> >>>           */
> >>> -        align = (unsigned long)skb->data & 3;
> >>> +        align = ((unsigned long)(skb->data + sizeof(struct ethhdr))) 
> >>> & 3;
> >>>          if (align) {
> >>>              if (WARN_ON(skb_headroom(skb) < 3)) {
> >>>                  dev_kfree_skb(skb);
> >>
> >> Uhm, can you give a more verbose explanation? Without that I'd say 
> >> this patch is plain wrong.
> >> What the hell does struct ethhdr have to do with wireless?
> >  > This is not ethernet. It's 802.11. There is no such thing as an
> >  > ethernet header in a 802.11 packet.
> >  >
> > Where are in ieee80211_deliver_skb that is called after 
> > ieee80211_data_to_8023. So it is not 802.11.
> > 
> Do you want more explanation ?

No reply always means "ok" on this list ;)

-- 
Greetings, Michael.

Re: mac80211 : fix unaligned rx skb

[John W. Linville]

On Sun, Jun 07, 2009 at 11:26:22AM +0200, Michael Buesch wrote:
> On Sunday 07 June 2009 11:24:48 matthieu castet wrote:
> > matthieu castet wrote:

> > > Where are in ieee80211_deliver_skb that is called after 
> > > ieee80211_data_to_8023. So it is not 802.11.
> > > 
> > Do you want more explanation ?
> 
> No reply always means "ok" on this list ;)

Probably true...however, I was hoping to see an ACK from Johannes...

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.