Subject: Re: 3.9.5+: Crash in tcp_input.c:4810.

From: Ben Greear <[email-masked]>
Date: Mon, 08 Jul 2013 13:17:45 -0700

On 07/08/2013 01:10 PM, Eric Dumazet wrote:
> On Mon, 2013-07-08 at 12:59 -0700, Ben Greear wrote:
>
>>> There is this thing in ath9k about aggregating two frags
>>>
>>> drivers/net/wireless/ath/ath9k/recv.c line 1298 contains :
>>>
>>> RX_STAT_INC(rx_frags);
>>>
>>> Could you check these stats (I do not know if they are reported by
>>> ethtool -S or another debugging facility) and check if rx_frags is ever
>>> increasing ?
>>
>> They are in debugfs, and they appear to increase fairly often, for
>> instance:
>>
>> [root@lec2010-ath9k-1 lanforge]# cat /debug/ieee80211/wiphy0/ath9k/recv|tail -5
>>              RX-Pkts-All :  288009442
>>             RX-Bytes-All : 4067932166
>>               RX-Beacons :   14826735
>>                 RX-Frags :       3944
>>              RX-Spectral :          0
>>
>> I don't have the stats from the system that reproduced the bug
>> (it has been rebooted), but if I do see the bug again, I'll
>> grab the rx-frags and other stats just in case it shows
>> some anomaly.
>>
>
> Reading this code again, I believe following patch is needed.
>
> Could you test it ?

Sure, will do.  Adding the linux-wireless mailing list as well.

Thanks,
Ben

>
> Thanks
>
> diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
> index 8be2b5d..f642f04 100644
> --- a/drivers/net/wireless/ath/ath9k/recv.c
> +++ b/drivers/net/wireless/ath/ath9k/recv.c
> @@ -1317,7 +1317,8 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
>   		if (sc->rx.frag) {
>   			int space = skb->len - skb_tailroom(hdr_skb);
>
> -			if (pskb_expand_head(hdr_skb, 0, space, GFP_ATOMIC) < 0) {
> +			if (space > 0 &&
> +			    pskb_expand_head(hdr_skb, 0, space, GFP_ATOMIC) < 0) {
>   				dev_kfree_skb(skb);
>   				RX_STAT_INC(rx_oom_err);
>   				goto requeue_drop_frag;
>

-- 
Ben Greear <[email-masked]>
Candela Technologies Inc  http://www.candelatech.com