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

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Message-ID: <20121129103744.38149dc6@thirdoffive.cmf.nrl.navy.mil>
Date:	Thu, 29 Nov 2012 10:37:44 -0500
From:	chas williams - CONTRACTOR <chas@....nrl.navy.mil>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	David Laight <David.Laight@...LAB.COM>,
	Krzysztof Mazur <krzysiek@...lesie.net>, 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 Wed, 28 Nov 2012 22:18:35 +0000
David Woodhouse <dwmw2@...radead.org> wrote:


> diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
> index 9851093..3720670 100644
> --- a/drivers/atm/solos-pci.c
> +++ b/drivers/atm/solos-pci.c
> @@ -92,6 +92,7 @@ struct pkt_hdr {
>  };
>  
>  struct solos_skb_cb {
> +	struct completion c;
>  	struct atm_vcc *vcc;
>  	uint32_t dma_addr;
>  };
> @@ -881,11 +882,18 @@ static void pclose(struct atm_vcc *vcc)
>  	header->vci = cpu_to_le16(vcc->vci);
>  	header->type = cpu_to_le16(PKT_PCLOSE);
>  
> +	init_completion(&SKB_CB(skb)->c);
> +
>  	fpga_queue(card, SOLOS_CHAN(vcc->dev), skb, NULL);
>  
>  	clear_bit(ATM_VF_ADDR, &vcc->flags);
>  	clear_bit(ATM_VF_READY, &vcc->flags);

you shouldnt clear ATM_VF_ADDR until the vpi/vci is actually closed and
ready for reuse.  at this point, it isnt. ATM_VF_READY should already
be clear at this point but you should set it before you queue your
PKT_CLOSE.  these flags probably should be handled outside the drivers
since the context for them is pretty clear.  just another patch i never
got around to writing...

checking for ATM_VF_READY in find_vcc() is probably going to give you
grief as well since ATM_VF_READY isnt entirely under your control.  you
need to be able to find the vcc until after pclose() is finished since
your tasklet might have a few packets it is still processing?
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