From: Andy Lutomirski <luto@kernel.org>

Date: Sun, 28 May 2017 10:00:11 -0700

Subject: x86/mm: Change the leave_mm() condition for local TLB flushes

Git-commit: 59f537c1dea04287165bb11407921e095250dc80

Patch-mainline: v4.13-rc1

References: bsc#1068032 CVE-2017-5754

On a remote TLB flush, we leave_mm() if we're TLBSTATE_LAZY.  For a

local flush_tlb_mm_range(), we leave_mm() if !current->mm.  These

are approximately the same condition -- the scheduler sets lazy TLB

mode when switching to a thread with no mm.

I'm about to merge the local and remote flush code, but for ease of

verifying and bisecting the patch, I want the local and remote flush

behavior to match first.  This patch changes the local code to match

the remote code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>

Acked-by: Rik van Riel <riel@redhat.com>

Cc: Andrew Morton <akpm@linux-foundation.org>

Cc: Arjan van de Ven <arjan@linux.intel.com>

Cc: Borislav Petkov <bpetkov@suse.de>

Cc: Dave Hansen <dave.hansen@intel.com>

Cc: Linus Torvalds <torvalds@linux-foundation.org>

Cc: Mel Gorman <mgorman@suse.de>

Cc: Michal Hocko <mhocko@suse.com>

Cc: Nadav Amit <nadav.amit@gmail.com>

Cc: Nadav Amit <namit@vmware.com>

Cc: Peter Zijlstra <peterz@infradead.org>

Cc: Rik van Riel <riel@redhat.com>

Cc: Thomas Gleixner <tglx@linutronix.de>

Cc: linux-mm@kvack.org

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Acked-by: Borislav Petkov <bp@suse.de>

---

 arch/x86/mm/tlb.c |    2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/mm/tlb.c

+++ b/arch/x86/mm/tlb.c

@@ -311,7 +311,7 @@ void flush_tlb_mm_range(struct mm_struct

 		goto out;

 	}

-	if (!current->mm) {

+	if (this_cpu_read(cpu_tlbstate.state) != TLBSTATE_OK) {

 		leave_mm(smp_processor_id());

 		/* Synchronize with switch_mm. */