netdev - Re: [PATCH net-next 2/2] mac80211: Resolve sk_refcnt/sk_wmem

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Message-ID: <54116D8E.20308@broadcom.com>
Date:	Thu, 11 Sep 2014 11:38:22 +0200
From:	Arend van Spriel <arend@...adcom.com>
To:	Johannes Berg <johannes@...solutions.net>
CC:	Alexander Duyck <alexander.h.duyck@...el.com>,
	<netdev@...r.kernel.org>, <linux-wireless@...r.kernel.org>,
	<davem@...emloft.net>, <eric.dumazet@...il.com>,
	<linville@...driver.com>
Subject: Re: [PATCH net-next 2/2] mac80211: Resolve sk_refcnt/sk_wmem_alloc
 issue in wifi ack path

On 09/11/14 09:06, Johannes Berg wrote:
> On Wed, 2014-09-10 at 18:05 -0400, Alexander Duyck wrote:
>> There is a possible issue with the use, or lack thereof of sk_refcnt and
>> sk_wmem_alloc in the wifi ack status functionality.
>>
>> Specifically if a socket were to request acknowledgements, and the socket
>> were to have sk_refcnt drop to 0 resulting in it waiting on sk_wmem_alloc
>> to reach 0 it would be possible to have sock_queue_err_skb orphan the last
>> buffer, resulting in __sk_free being called on the socket.  After this the
>> buffer is enqueued on sk_error_queue, however the queue has already been
>> flushed resulting in at least a memory leak, if not a data corruption.
>
> Oh. Thanks :-)

Hi Alexander,

So why is this only an issue in wifi ack path. The sock_queue_err_skb() 
does not mention the caller should hold a sock reference. This seems 
entirely an issue of the sock_queue_err_skb() function itself so why not 
do sk_hold/sk_put within that function. Does it impose too much overhead?

Regards,
Arend
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