linux-kernel - Re: [PATCH v3 1/9] x86/microcode/AMD: subtract SECTION_HDR

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Date:   Wed, 14 Mar 2018 13:38:51 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/9] x86/microcode/AMD: subtract SECTION_HDR_SIZE from
 file leftover length

On Tue, Mar 13, 2018 at 10:06:10PM +0100, Maciej S. Szmigiero wrote:
> verify_patch_size() function verifies whether the microcode container file
> remaining size is large enough to contain a patch of the indicated size.
> 
> However, the section header length is not included in this indicated size
> but it is present in the leftover file length so it should be subtracted
> from the leftover file length before passing this value to
> verify_patch_size().
> 
> Signed-off-by: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
> ---
>  arch/x86/kernel/cpu/microcode/amd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> index a998e1a7d46f..ffe0d0ce57fc 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -613,7 +613,8 @@ static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover)
>  		return crnt_size;
>  	}
>  
> -	ret = verify_patch_size(family, patch_size, leftover);
> +	ret = verify_patch_size(family, patch_size,
> +				leftover - SECTION_HDR_SIZE);

Pls add a sentence or two as a comment above it explaining why the
section header size needs to be subtracted and do not break the line
even if it is > 80 cols.

Thx.

-- 
Regards/Gruss,
    Boris.

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