Re: [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

[Kees Cook]

On Fri, Mar 4, 2016 at 8:25 AM, Baoquan He <bhe@xxxxxxxxxx> wrote:
> When process 32 bit relocation tables a local variable 'extended'
> is defined to calculate the physical address of relocs entry.
> However its type is 'int' which is enough for i386, but not enough
> for x86_64. That's why relocation can only be handled under 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.
>
> Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

This patch should probably be moved up into the start of this series
instead of living in the middle here, since it's a clear stand-alone
bug fix.

-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 4b2cd0c..70445c3 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -298,7 +298,7 @@ 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;
> --
> 2.5.0
>



-- 
Kees Cook
Chrome OS & Brillo Security