linux-kernel - Re: [PATCHv2] Fix EDD3.0 data verification.

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Date:	Wed, 16 Feb 2011 17:09:33 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Subject: Re: [PATCHv2] Fix EDD3.0 data verification.

On Tue, Feb 08, 2011 at 04:53:01PM +0200, Gleb Natapov wrote:
> Peter, ping.
> 
> Is this version acceptable?
> 
Ping?

> On Thu, Feb 03, 2011 at 02:29:48PM +0200, Gleb Natapov wrote:
> > Check for nonzero path in edd_has_edd30() has no sense. First, it looks
> > at the wrong memory. Device path starts at offset 30 of the info->params
> > structure which is at offset 8 from the beginning of info structure, but
> > code looks at info + 4 instead. This was correct when code was introduced,
> > but around v2.6.4 three more fields were added to edd_info structure
> > (commit 66b61a5c in history.git). Second, even if it will check correct
> > memory it will always succeed since at offset 30 (params->key) there will
> > be non-zero values otherwise previous check would fail.
> > 
> > The patch replaces this bogus check with one that verifies checksum.
> > 
> > Signed-off-by: Gleb Natapov <gleb@...hat.com>
> > ---
> > v1->v2
> >   use device path info length to calculate csum.
> > 
> > diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
> > index 96c25d9..f1b7f65 100644
> > --- a/drivers/firmware/edd.c
> > +++ b/drivers/firmware/edd.c
> > @@ -531,8 +531,8 @@ static int
> >  edd_has_edd30(struct edd_device *edev)
> >  {
> >  	struct edd_info *info;
> > -	int i, nonzero_path = 0;
> > -	char c;
> > +	int i;
> > +	u8 csum = 0;
> >  
> >  	if (!edev)
> >  		return 0;
> > @@ -544,16 +544,16 @@ edd_has_edd30(struct edd_device *edev)
> >  		return 0;
> >  	}
> >  
> > -	for (i = 30; i <= 73; i++) {
> > -		c = *(((uint8_t *) info) + i + 4);
> > -		if (c) {
> > -			nonzero_path++;
> > -			break;
> > -		}
> > -	}
> > -	if (!nonzero_path) {
> > +
> > +	/* We support only T13 spec */
> > +	if (info->params.device_path_info_length != 44)
> > +		return 0;
> > +
> > +	for (i = 30; i < info->params.device_path_info_length + 30; i++)
> > +		csum += *(((u8 *)&info->params) + i);
> > +
> > +	if (csum)
> >  		return 0;
> > -	}
> >  
> >  	return 1;
> >  }
> > --
> > 			Gleb.
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> 
> --
> 			Gleb.
> --
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--
			Gleb.
--
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