From 16882484f96f9d75348904bd5a4e2a53acb67378 Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Mon, 25 Jun 2018 16:49:47 -0700
Subject: Check for empty applicationAddrRange in MM.DecUsers.

PiperOrigin-RevId: 202043776
Change-Id: I4373abbcf735dc1cf4bebbbbb0c7124df36e9e78
---
 pkg/sentry/mm/lifecycle.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pkg/sentry/mm/lifecycle.go b/pkg/sentry/mm/lifecycle.go
index de7f29b04..a4b5cb443 100644
--- a/pkg/sentry/mm/lifecycle.go
+++ b/pkg/sentry/mm/lifecycle.go
@@ -214,5 +214,9 @@ func (mm *MemoryManager) DecUsers(ctx context.Context) {
 
 	mm.mappingMu.Lock()
 	defer mm.mappingMu.Unlock()
-	mm.unmapLocked(ctx, mm.applicationAddrRange())
+	// If mm is being dropped before mm.SetMmapLayout was called,
+	// mm.applicationAddrRange() will be empty.
+	if ar := mm.applicationAddrRange(); ar.Length() != 0 {
+		mm.unmapLocked(ctx, ar)
+	}
 }
-- 
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