linux-kernel - Re: [PATCH 12/42] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

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Date:	Tue, 7 Jul 2015 15:42:56 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/42] x86, kaslr: Fix a bug that relocation can not be
 handled when kernel is loaded above 2G

On Tue, Jul 7, 2015 at 1:19 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> From: Baoquan He <bhe@...hat.com>
>
> When process 32 bit relocation tables a local variable extended is
> defined to calculate the physical address of relocs entry. However
> it's type is int which is enough for i386, for x86_64 not enough.
> That's why relocation can only be handled when kernel is loaded
> below 2G, otherwise a overflow will happen and cause system hang.
>
> Here change it to long as 32 bit inverse relocation processing does,
> and this change is safe for i386 relocation handling too.
>
> Signed-off-by: Baoquan He <bhe@...hat.com>

This looks right, thanks!

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  arch/x86/boot/compressed/misc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 83f98a5..bfa4f0a 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -273,7 +273,7 @@ static void handle_relocations(void *output, unsigned long output_len)
>          * So we work backwards from the end of the decompressed image.
>          */
>         for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
> -               int extended = *reloc;
> +               long extended = *reloc;
>                 extended += map;
>
>                 ptr = (unsigned long)extended;
> --
> 1.8.4.5
>



-- 
Kees Cook
Chrome OS Security
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