linux-kernel - Re: [PATCH] x86: boot: Fix EFI stub alignment

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Date:   Tue, 18 Sep 2018 15:04:54 -0700
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Ben Hutchings <ben@...adent.org.uk>
Cc:     "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH] x86: boot: Fix EFI stub alignment

On 16 September 2018 at 08:22, Ben Hutchings <ben@...adent.org.uk> wrote:
> We currently align the end of the compressed image to a multiple of
> 16.  However the PE-COFF header included in the EFI stub says that the
> file alignment is 32 bytes, and when adding an EFI signature to the
> file it must first be padded to this alignment.
>
> sbsigntool commands warn about this:
>
>     warning: file-aligned section .text extends beyond end of file
>     warning: checksum areas are greater than image size. Invalid section table?
>
> Worse, pesign-at least when creating a detached signature—uses the
> hash of the unpadded file, resulting in an invalid signature if
> padding is required.
>
> Avoid both these problems by increasing alignment to 32 bytes when
> CONFIG_EFI_STUB is enabled.
>
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> ---

Thanks, queued in efi/next.


> --- a/arch/x86/boot/tools/build.c
> +++ b/arch/x86/boot/tools/build.c
> @@ -391,6 +391,13 @@ int main(int argc, char ** argv)
>                 die("Unable to mmap '%s': %m", argv[2]);
>         /* Number of 16-byte paragraphs, including space for a 4-byte CRC */
>         sys_size = (sz + 15 + 4) / 16;
> +#ifdef CONFIG_EFI_STUB
> +       /*
> +        * COFF requires minimum 32-byte alignment of sections, and
> +        * adding a signature is problematic without that alignment.
> +        */
> +       sys_size = (sys_size + 1) & ~1;
> +#endif
>
>         /* Patch the setup code with the appropriate size parameters */
>         buf[0x1f1] = setup_sectors-1;