Re: [TIP] BUG kmalloc-4096: Poison overwritten (ath5k_rx_skb_alloc)

[pat-lkml]

On Mon, 23 Feb 2009 18:03:16 +0200, Nick Kossifidis <mickflemm@xxxxxxxxx>
wrote:
> 2009/2/23 Bob Copeland <me@xxxxxxxxxxxxxxx>:
>> On Mon, 23 Feb 2009 00:20:50 +0100, Jiri Slaby wrote
>>> On 22.2.2009 22:56, Jiri Slaby wrote:
>>> > Well, maybe we should try to reproduce with jumbo packets sent to the
>>> > ath5k receiver, since I think it (1) is not very much test-covered
>>> > code
>>> > (2) appears to be related.
>>>
>>> According to the spec I have for older chip, there is not `done' flag
>>> set for descriptors which have `more' flag set. We handle this wrongly.
>>> Am I looking correctly, Nick, Luis, Bob?
>>>
>>> I still don't see what could have caused this though.
>>
>> As I understand it, yes, we don't do the right thing when the more flag
>> is set.  We're supposed to keep processing packets until we get one with
>> the done flag, and then all of that is supposed to be merged into a
>> single
>> packet.  Other flags such as the rx rate are only valid on the final
>> packet.
>>
>> However, I did some debugging of this a while ago and concluded that the
>> 'jumbo' frames were largely garbage data.  The dma buffer size is
>> certainly
>> large enough for a standard 802.11 frame and the 'more' flag is only
>> supposed to be set if the dma buffer size is too small for a packet.  In
>> all cases the dma buffer size was 2500+ bytes and the actual contents of
>> the packets looked like random values (I did have encryption turned on,
>> but there were no 802.11 headers I could see.)
>>
>> So I am not sure if the jumbo packets are causing bad things to happen,
>> or if they are an indication that something bad has already happened.
>>
> 
> Hmm can someone test ath5k against an Atheros AP using fast frames ?
> Maybe they are jumbo frames but they don't have any header etc so that
> they look like one frame after un-fragmentation, documentation says
> that the current frame is continued in the next descriptor if more is
> set to 1 so i guess next buffer might not have the header. If more = 0
> then it's our last descriptor and only then other fields such as done,
> frame receive ok, rssi etc are valid.

If an ath9k device in AP mode using hostapd counts as an Atheros AP, then I

can test tonight.  If you can send me the steps to test this, I'll do it in

about 8 hours.

Pat Erley
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