linux-kernel - Re: Regression associated with commit c8628155ece3

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Date:	Fri, 24 Aug 2012 18:23:52 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Larry Finger <Larry.Finger@...inger.net>
Cc:	David Miller <davem@...emloft.net>, ncardwell@...gle.com,
	linville@...driver.com, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Regression associated with commit c8628155ece3 - "tcp: reduce
 out_of_order memory use"

On Fri, 2012-08-24 at 18:18 +0200, Eric Dumazet wrote:
> On Fri, 2012-08-24 at 10:58 -0500, Larry Finger wrote:
> > On 08/24/2012 10:19 AM, David Miller wrote:
> > >
> > > This looks like full-on data corruption to me.
> > 
> > I agree. The question is why does it happen with r8712u, and only after the 
> > commit in the subject. Drivers for other devices that I have are OK. Thus far, I 
> > have tested b43, rtl8187, ath9k_htc, and rtl8192cu. To my knowledge, there are 
> > no reports posted for this bug with any other device.
> 
> bugs can sit unnoticed, and one change somewhere can uncover them.
> 
> Really this driver must have a bug, if not half a dozen of bugs.
> 
> For example this sequence of code is a clear bug :
> 
> sub_skb = dev_alloc_skb(nSubframe_Length + 12); 
> skb_reserve(sub_skb, 12);
> 
> 
> Also the free_recv_skb_queue looks really suspect to me
> 
> What the hell is doing recv_tasklet() I really wonder.
> 
> This code, combined with the skb_clone() in recvbuf2recvframe()
> can clearly reuse an skb passed to upper stacks.
> 
> 
> queueing one skb in free_recv_skb_queue should be done
> only if no clone of this skb exist somewhere.
> 
> Please someone fix this buggy driver.
> 

Try the following patch for a start

diff --git a/drivers/staging/rtl8712/rtl8712_recv.c b/drivers/staging/rtl8712/rtl8712_recv.c
index 8e82ce2..88e3ca6 100644
--- a/drivers/staging/rtl8712/rtl8712_recv.c
+++ b/drivers/staging/rtl8712/rtl8712_recv.c
@@ -1127,6 +1127,9 @@ static void recv_tasklet(void *priv)
 		recvbuf2recvframe(padapter, pskb);
 		skb_reset_tail_pointer(pskb);
 		pskb->len = 0;
-		skb_queue_tail(&precvpriv->free_recv_skb_queue, pskb);
+		if (!skb_cloned(pskb))
+			skb_queue_tail(&precvpriv->free_recv_skb_queue, pskb);
+		else
+			consume_skb(pskb);
 	}
 }


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