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. */