From 8416da33d25bf28cfcfdcbe658f696d6883eebcd Mon Sep 17 00:00:00 2001
From: gVisor bot <gvisor-bot@google.com>
Date: Tue, 5 May 2020 17:57:22 -0700
Subject: Internal change.

PiperOrigin-RevId: 310057834
---
 pkg/sentry/pgalloc/pgalloc.go | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'pkg/sentry')

diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go
index 577e9306a..2b11ea4ae 100644
--- a/pkg/sentry/pgalloc/pgalloc.go
+++ b/pkg/sentry/pgalloc/pgalloc.go
@@ -180,6 +180,11 @@ type MemoryFileOpts struct {
 	// notifications to determine when eviction is necessary. This option has
 	// no effect unless DelayedEviction is DelayedEvictionEnabled.
 	UseHostMemcgPressure bool
+
+	// If ManualZeroing is true, MemoryFile must not assume that new pages
+	// obtained from the host are zero-filled, such that MemoryFile must manually
+	// zero newly-allocated pages.
+	ManualZeroing bool
 }
 
 // DelayedEvictionType is the type of MemoryFileOpts.DelayedEviction.
@@ -432,6 +437,15 @@ func (f *MemoryFile) Allocate(length uint64, kind usage.MemoryKind) (platform.Fi
 
 	// Mark selected pages as in use.
 	fr := platform.FileRange{start, end}
+	if f.opts.ManualZeroing {
+		if err := f.forEachMappingSlice(fr, func(bs []byte) {
+			for i := range bs {
+				bs[i] = 0
+			}
+		}); err != nil {
+			return platform.FileRange{}, err
+		}
+	}
 	if !f.usage.Add(fr, usageInfo{
 		kind: kind,
 		refs: 1,
-- 
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