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SubjectRe: [tip:x86/boot] x86/mm: Enable KASLR for physical mapping memory regions
On Tue, Aug 16, 2016 at 10:50 AM, Borislav Petkov <bp@alien8.de> wrote:
> On Tue, Aug 16, 2016 at 05:54:12PM +0200, Borislav Petkov wrote:
>> Ok, I ran this in a guest and it finds the microcode patches properly.
>
> Here's a better version to take care of the APs too:
>
> ---
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> index 27a0228c9cae..05242322e324 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -355,6 +355,7 @@ void load_ucode_amd_ap(void)
> unsigned int cpu = smp_processor_id();
> struct equiv_cpu_entry *eq;
> struct microcode_amd *mc;
> + u8 *cont;
> u32 rev, eax;
> u16 eq_id;
>
> @@ -371,8 +372,12 @@ void load_ucode_amd_ap(void)
> if (check_current_patch_level(&rev, false))
> return;
>
> +#ifdef CONFIG_RANDOMIZE_MEMORY
> + cont = container + PAGE_OFFSET - __PAGE_OFFSET_BASE;
> +#endif
> +
> eax = cpuid_eax(0x00000001);
> - eq = (struct equiv_cpu_entry *)(container + CONTAINER_HDR_SZ);
> + eq = (struct equiv_cpu_entry *)(cont + CONTAINER_HDR_SZ);

Am I misreading this? Shouldn't it be:

cont = container;
#ifdef CONFIG_RANDOMIZE_MEMORY
cont += PAGE_OFFSET - __PAGE_OFFSET_BASE;
#endif

(otherwise cont is undefined in the RANDOMIZE_MEMORY=n case?)

>
> eq_id = find_equiv_id(eq, eax);
> if (!eq_id)
> @@ -434,6 +439,10 @@ int __init save_microcode_in_initrd_amd(void)
> else
> container = cont_va;
>
> +#ifdef CONFIG_RANDOMIZE_MEMORY
> + container += PAGE_OFFSET - __PAGE_OFFSET_BASE;
> +#endif
> +
> eax = cpuid_eax(0x00000001);
> eax = ((eax >> 8) & 0xf) + ((eax >> 20) & 0xff);
>
>
> --
> Regards/Gruss,
> Boris.
>
> ECO tip #101: Trim your mails when you reply.
> --


-Kees

--
Kees Cook
Nexus Security

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