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From: Andrew Chant <andrew.chant@gmail.com>
Date: Fri, 6 Jul 2012 00:46:42 -0700
Message-ID: <CANugF35qjKLdhBprQviNJaAPfM910wFCSbyEvdcCRj_UoKLqPQ@mail.gmail.com> (sfid-20120706_094727_997866_A5F431DC)
Subject: Re: v3.4.4 ath9k: kernel NULL pointer dereference in skb_dequeue
 during heavy udp xmit
To: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-wireless@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@gmail.com>,
	Jouni Malinen <jouni@qca.qualcomm.com>,
	Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>,
	Senthil Balasubramanian <senthilb@qca.qualcomm.com>
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Sender: linux-wireless-owner@vger.kernel.org

I was able to reproduce this on a boot shortly afterwards without
changing the frequencies.
Exact same stack trace w/ exception of slightly different values for
RBX & R15, and R10 had 0x7f instead of 0x80.  I have not been able to
reproduce since despite trying quite hard :)  I have a picture of the
second oops if that helps.
PCI ID is 168c:0030 (AR9300 Wireless LAN adaptor (rev 01))
-Andrew

On Fri, Jul 6, 2012 at 12:15 AM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> -John
> +QCA folks
>
> On Thu, 2012-07-05 at 21:36 -0700, Andrew Chant wrote:
>
>>  while performance testing ath9k -> ath9k performance in 3.4.4, I got
>> a nasty kernel panic.  My performance testing involved filling the air
>> with 1410-byte UDP packets between the machines, and switching the
>> frequencies of the two cards to see how frequency affected
>> performance.  I had switched between channels 36, 40, 44, and 48.
>> Oops was on the transmitting machine, which was acting as the AP.
>>
>> Very clear screen image of the oops is at
>> https://picasaweb.google.com/lh/photo/CjBdHLZH0up5PrnmCySJidMTjNZETYmyPJy0liipFm0?feat=directlink
>
> I briefly looked at this, but I don't see a bug in mac80211. It seems
> likely that ath9k hands back a corrupted SKB, or frees one it no longer
> owns, or such. The skb->next/prev pointers seem corrupted (rcx is NULL)
> in one of the SKBs on the list, but mac80211 can't do that afaict.
>
> johannes
>