From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Sat, 12 May 2018 00:16:26 +0000 (-0400)
Subject: x86/bugs/IBRS: Warn if IBRS is enabled during boot.
X-Git-Tag: v4.1.12-124.31.3~779
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=35e2983d16be6183f03841d8167fde9bd81413cf;p=users%2Fjedix%2Flinux-maple.git

x86/bugs/IBRS: Warn if IBRS is enabled during boot.

It should never be. But in case it is lets warn and clear it.

OraBug: 28041771
CVE: CVE-2018-3639

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Mihai Carabas <mihai.carabas@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/arch/x86/kernel/cpu/bugs_64.c b/arch/x86/kernel/cpu/bugs_64.c
index 2b83e8899a0b..ec6df4448c94 100644
--- a/arch/x86/kernel/cpu/bugs_64.c
+++ b/arch/x86/kernel/cpu/bugs_64.c
@@ -123,7 +123,10 @@ void __init check_bugs(void)
 	 */
        if (boot_cpu_has(X86_FEATURE_IBRS)) {
 		rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
-
+		if (x86_spec_ctrl_base & SPEC_CTRL_IBRS) {
+			pr_warn("SPEC CTRL MSR (0x%16llx) has IBRS set during boot, clearing it.", x86_spec_ctrl_base);
+			x86_spec_ctrl_base &= ~(SPEC_CTRL_IBRS);
+		}
 		x86_spec_ctrl_priv = x86_spec_ctrl_base;
 	}