linux-kernel - Re: [PATCH v2 3/3] pppoatm: protect against freeing of vcc

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Message-ID: <20121129162818.GA6615@shrek.podlesie.net>
Date:	Thu, 29 Nov 2012 17:28:18 +0100
From:	Krzysztof Mazur <krzysiek@...lesie.net>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	David Laight <David.Laight@...LAB.COM>,
	chas williams - CONTRACTOR <chas@....nrl.navy.mil>,
	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, nathan@...verse.com.au
Subject: Re: [PATCH v2 3/3] pppoatm: protect against freeing of vcc

On Thu, Nov 29, 2012 at 03:47:57PM +0000, David Woodhouse wrote:
> On Thu, 2012-11-29 at 16:09 +0100, Krzysztof Mazur wrote:
> > 
> > I don't like two thinks about this patch:
> > 
> >         - if allos_skb(sizeof(*header), GFP_ATOMIC) at beginning of
> >           pclose() fails we will crash
> > 
> >         - if card wakes up after this timeout we will probably crash too
> > 
> > That's why proposed different approach, but it has other problems.
> 
> How about this variant on what you suggested. Yes, we can definitely
> remove everything that's in the queue... as long as we use
> skb_queue_walk_safe() instead of skb_queue_walk().
> 
> We can use GFP_KERNEL instead of GFP_ATOMIC, which at least reduces the
> likelihood of failing to close the vcc.
> 
> We end up waiting *only* if there is a packet which is *currently* being
> DMA'd to the card. And if the card doesn't take that within 5 seconds,
> it almost certainly never will. So I can live with that.
> 

Yeah, that shouldn't happen.

> +				if (!test_bit(ATM_VF_READY, &vcc->flags))
> +					wake_up(&card->param_wq);
> +			} else

according to CodingStyle:

+ } else {
>  				dev_kfree_skb_irq(oldskb);
> -			}
+ }

Krzysiek
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