netdev - Re: [PATCH v2 net] can: sja1000: fix use after free in ems_pcmcia_add

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Date:   Wed, 24 Nov 2021 08:37:27 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Wolfgang Grandegger <wg@...ndegger.com>
Cc:     Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Leon Romanovsky <leon@...nel.org>,
        Markus Plessing <plessing@...-wuensche.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2 net] can: sja1000: fix use after free in
 ems_pcmcia_add_card()

Hello Dan,

On 24.11.21 07:56, Dan Carpenter wrote:
> If the last channel is not available then "dev" is freed.  Fortunately,
> we can just use "pdev->irq" instead.

But in the case that we do not find any channel the irq for the card is 
still requested (via pdev->irq).

> 
> Fixes: fd734c6f25ae ("can/sja1000: add driver for EMS PCMCIA card")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> v2: In the first version, I just failed the probe.  Sorry about that.
> 
>   drivers/net/can/sja1000/ems_pcmcia.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/sja1000/ems_pcmcia.c b/drivers/net/can/sja1000/ems_pcmcia.c
> index e21b169c14c0..391a8253ed6f 100644
> --- a/drivers/net/can/sja1000/ems_pcmcia.c
> +++ b/drivers/net/can/sja1000/ems_pcmcia.c
> @@ -234,7 +234,7 @@ static int ems_pcmcia_add_card(struct pcmcia_device *pdev, unsigned long base)
>   			free_sja1000dev(dev);
>   	}
>   
> -	err = request_irq(dev->irq, &ems_pcmcia_interrupt, IRQF_SHARED,

When adding this check, we should be fine:

+	if (card->channels)

> +	err = request_irq(pdev->irq, &ems_pcmcia_interrupt, IRQF_SHARED,
>   			  DRV_NAME, card);
>   	if (!err)
>   		return 0;
> 

Thanks for checking this code after so many years!

I saved that 17 year old EMS PCMCIA Card from my former CAN hardware box 
two weeks ago and made a 5.16-rc2 run on a 2006 Samsung X20 with Pentium 
M 1.7GHz yesterday. My only machine here at home with a PCMCIA slot :-D

https://www.amazon.de/Samsung-Centrino-1-73GHz-Graphic-Accelerator/dp/B000AXSIRE

And it still works with the CAN card!

Best regards,
Oliver