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SubjectRe: [TIP] BUG kmalloc-4096: Poison overwritten (ath5k_rx_skb_alloc)
From
2009/2/23  <pat-lkml@erley.org>:
> On Mon, 23 Feb 2009 18:03:16 +0200, Nick Kossifidis <mickflemm@gmail.com>
> wrote:
>> 2009/2/23 Bob Copeland <me@bobcopeland.com>:
>>> 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
>

As far as i know ath9k doesn't support fast frames ;-(

--
GPG ID: 0xD21DB2DB
As you read this post global entropy rises. Have Fun ;-)
Nick


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