[MODERATED] Re: [PATCH v3 06/10] [PATCH v3 6/9] Linux Patch #6

[Borislav Petkov <bp@suse.de>]

On Mon, Apr 23, 2018 at 08:57:55PM +0200, Borislav Petkov wrote:
> Something's still fishy with this patch. I'm booting a guest with
> 
> spec_store_bypass_disable=on
> 
> but dmesg still says:
> 
> [    0.044001] Speculative Store Bypass: Vulnerable

Ok, there it is:

static enum spec_store_bypass_mitigation_cmd __init spec_store_bypass_parse_cmdline(void)
{
        char arg[20];
        int ret, i;
        enum spec_store_bypass_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;

        if (!boot_cpu_has_bug(X86_BUG_CPU_SPEC_STORE_BYPASS)) {
                return SPEC_STORE_BYPASS_CMD_NONE;

It needs to be

	if (!boot_cpu_has_bug(X86_BUG_CPU_SPEC_STORE_BYPASS))

not

	if (!boot_cpu_has(X86_FEATURE_STBUF_BYPASS))

which we set earlier in cpu_set_bug_bits().

Which makes me wonder why we even need X86_FEATURE_STBUF_BYPASS?

Or why we need X86_BUG_CPU_SPEC_STORE_BYPASS?

One of the two is superfluous AFAICT.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--