linux-kernel - Re: AMD microcode loading broken on 32 bit

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Date:	Tue, 28 Jan 2014 16:37:19 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: AMD microcode loading broken on 32 bit

On 01/28/2014 04:30 PM, Borislav Petkov wrote:
> On Tue, Jan 28, 2014 at 04:05:20PM -0500, Boris Ostrovsky wrote:
>> Yes. This was a bug in our build environment. It is fixed now but I
>> put this bug back when I was testing your patch.
> Right, that was the deal. Oh well, we'd need to verify the container
> too, I guess:

I'll give it a spin. Apparently the problem is currently in 
install_equiv_cpu_table()
when we are trying to index into buf and buf (which is container) 
doesn't appear
to be there.

Are you sure that

     container = (u8 *)(__va((u32)relocated_ramdisk) +
                            ((u32)container - 
boot_params.hdr.ramdisk_image));

in save_microcode_in_initrd_amd() always results in a valid pointer? It 
is non-NULL but it
points to address that looks to be not mapped.

-boris

>
> ---
> diff --git a/arch/x86/kernel/cpu/microcode/amd_early.c b/arch/x86/kernel/cpu/microcode/amd_early.c
> index 8384c0fa206f..c568b6c9af95 100644
> --- a/arch/x86/kernel/cpu/microcode/amd_early.c
> +++ b/arch/x86/kernel/cpu/microcode/amd_early.c
> @@ -37,10 +37,12 @@ static __initdata char ucode_path[] = "kernel/x86/microcode/AuthenticAMD.bin";
>   
>   static struct cpio_data __init find_ucode_in_initrd(void)
>   {
> +	struct cpio_data ret;
>   	long offset = 0;
>   	char *path;
>   	void *start;
>   	size_t size;
> +	u32 *hdr;
>   
>   #ifdef CONFIG_X86_32
>   	struct boot_params *p;
> @@ -59,7 +61,18 @@ static struct cpio_data __init find_ucode_in_initrd(void)
>   	size    = boot_params.hdr.ramdisk_size;
>   #endif
>   
> -	return find_cpio_data(path, start, size, &offset);
> +	ret = find_cpio_data(path, start, size, &offset);
> +
> +	/* Verify we didn't get some garbage from the initrd. */
> +	hdr = (u32 *)ret.data;
> +
> +	if (hdr[0] != UCODE_MAGIC ||
> +	    hdr[1] != UCODE_EQUIV_CPU_TABLE_TYPE ||
> +	    hdr[2] == 0) {
> +		ret.data = NULL;
> +		ret.size = 0;
> +	}
> +	return ret;
>   }
>   
>   static size_t compute_container_size(u8 *data, u32 total_size)
> @@ -359,7 +372,7 @@ int __init save_microcode_in_initrd_amd(void)
>   		pr_info("microcode: updated early to new patch_level=0x%08x\n",
>   			ucode_new_rev);
>   
> -	if (!container)
> +	if (!container || !ucode_cpio.data)
>   		return -EINVAL;
>   
>   	eax   = cpuid_eax(0x00000001);
> --
>

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