linux-kernel - Re: [Xen-devel] [PATCH 2/4] xen/hvc: Fix error cases around HVM_PARAM_CONSOLE

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Date:	Thu, 24 May 2012 11:47:12 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 2/4] xen/hvc: Fix error cases around
 HVM_PARAM_CONSOLE_PFN

On Wed, 23 May 2012, Konrad Rzeszutek Wilk wrote:
> We weren't resetting the parameter to be passed in to a
> known default. Nor were we checking the return value of
> hvm_get_parameter.
> 
> CC: stable@...nel.org
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>
>  drivers/tty/hvc/hvc_xen.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index afc7fc2..3277f0e 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -219,7 +219,8 @@ static int xen_hvm_console_init(void)
>  	if (r < 0)
>  		goto err;
>  	info->evtchn = v;
> -	hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
> +	v = 0;
> +	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
>  	if (r < 0)
>  		goto err;
>  	mfn = v;

Is 0 the right default here?
Maybe something invalid like (~0UL) would be better?
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