linux-kernel - [PATCH 4.14 04/14] x86/pti: Make sure the user/kernel PTEs match

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Date:   Thu,  4 Jan 2018 13:09:21 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Meelis Roos <mroos@...ux.ee>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH 4.14 04/14] x86/pti: Make sure the user/kernel PTEs match

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 52994c256df36fda9a715697431cba9daecb6b11 upstream.

Meelis reported that his K8 Athlon64 emits MCE warnings when PTI is
enabled:

[Hardware Error]: Error Addr: 0x0000ffff81e000e0
[Hardware Error]: MC1 Error: L1 TLB multimatch.
[Hardware Error]: cache level: L1, tx: INSN

The address is in the entry area, which is mapped into kernel _AND_ user
space. That's special because we switch CR3 while we are executing
there.

User mapping:
0xffffffff81e00000-0xffffffff82000000           2M     ro         PSE     GLB x  pmd

Kernel mapping:
0xffffffff81000000-0xffffffff82000000          16M     ro         PSE         x  pmd

So the K8 is complaining that the TLB entries differ. They differ in the
GLB bit.

Drop the GLB bit when installing the user shared mapping.

Fixes: 6dc72c3cbca0 ("x86/mm/pti: Share entry text PMD")
Reported-by: Meelis Roos <mroos@...ux.ee>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Meelis Roos <mroos@...ux.ee>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Tom Lendacky <thomas.lendacky@....com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801031407180.1957@nanos
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/mm/pti.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -367,7 +367,8 @@ static void __init pti_setup_espfix64(vo
 static void __init pti_clone_entry_text(void)
 {
 	pti_clone_pmds((unsigned long) __entry_text_start,
-			(unsigned long) __irqentry_text_end, _PAGE_RW);
+			(unsigned long) __irqentry_text_end,
+		       _PAGE_RW | _PAGE_GLOBAL);
 }
 
 /*