linux-kernel - Re: [PATCH 08/13] x86/microcode: Consolidate family,model, ... code

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Message-ID: <20150224162343.GH4565@chrystal.uk.oracle.com>
Date:	Tue, 24 Feb 2015 17:23:44 +0100
From:	Quentin Casasnovas <quentin.casasnovas@...cle.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH 08/13] x86/microcode: Consolidate family,model, ... code

On Tue, Feb 24, 2015 at 11:37:07AM +0100, Borislav Petkov wrote:
> @@ -159,42 +134,40 @@ static enum ucode_state
>  matching_model_microcode(struct microcode_header_intel *mc_header,
>  			unsigned long sig)
>  {
> -	u8 x86, x86_model;
> -	u8 x86_ucode, x86_model_ucode;
> +	unsigned int fam, model;
> +	unsigned int fam_ucode, model_ucode;
>  	struct extended_sigtable *ext_header;
>  	unsigned long total_size = get_totalsize(mc_header);
>  	unsigned long data_size = get_datasize(mc_header);
>  	int ext_sigcount, i;
>  	struct extended_signature *ext_sig;
>  
> -	x86 = get_x86_family(sig);
> -	x86_model = get_x86_model(sig);
> +	fam   = __x86_family(sig);
> +	model = x86_model(sig);
>  
> -	x86_ucode = get_x86_family(mc_header->sig);
> -	x86_model_ucode = get_x86_model(mc_header->sig);
> +	fam_ucode   = __x86_family(mc_header->sig);
> +	model_ucode = x86_model(mc_header->sig);
>  
> -	if (x86 == x86_ucode && x86_model == x86_model_ucode)
> +	if (fam == fam_ucode && model == model_ucode)
>  		return UCODE_OK;
>  
>  	/* Look for ext. headers: */
>  	if (total_size <= data_size + MC_HEADER_SIZE)
>  		return UCODE_NFOUND;
>  
> -	ext_header = (struct extended_sigtable *)
> -		     mc_header + data_size + MC_HEADER_SIZE;
> +	ext_header   = (struct extended_sigtable *)mc_header + data_size + MC_HEADER_SIZE;
> +	ext_sig      = (void *)ext_header + EXT_HEADER_SIZE;

I think we have another serious problem here, both in the original code and
in your patch - mc_header will first be casted to (unsigned long*) then
we'll add data_size and MC_HEADER_SIZE, potentially going way further than
intended.  Same remark for ext_sig.

Quentin
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