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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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  Re: [PATCH 12/42] x86, kaslr: Fix a bug that relocation can not be  handled when kernel is loaded above 2G Kees Cook <keescook@chromium.org> - 2015-07-08 00:50 +0200

#1179135 — 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@kernel.org> wrote:
> From: Baoquan He <bhe@redhat.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@redhat.com>

This looks right, thanks!

Acked-by: Kees Cook <keescook@chromium.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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