From c8b1f85493f9d1d141dd33cb88dfd435e17222b5 Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Thu, 8 Mar 2012 08:53:08 +1100
Subject: [PATCH] encoding/gob: fix memory corruption Fixes #3175.

R=golang-dev, iant, rsc, r
CC=golang-dev
https://golang.org/cl/5758069
---
 src/pkg/encoding/gob/decode.go         |  3 +++
 src/pkg/encoding/gob/gobencdec_test.go | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/pkg/encoding/gob/decode.go b/src/pkg/encoding/gob/decode.go
index 0708a83c99..e32a178aba 100644
--- a/src/pkg/encoding/gob/decode.go
+++ b/src/pkg/encoding/gob/decode.go
@@ -707,6 +707,9 @@ func (dec *Decoder) decodeInterface(ityp reflect.Type, state *decoderState, p ui
 	if name == "" {
 		// Copy the representation of the nil interface value to the target.
 		// This is horribly unsafe and special.
+		if indir > 0 {
+			p = allocate(ityp, p, 1) // All but the last level has been allocated by dec.Indirect
+		}
 		*(*[2]uintptr)(unsafe.Pointer(p)) = ivalue.InterfaceData()
 		return
 	}
diff --git a/src/pkg/encoding/gob/gobencdec_test.go b/src/pkg/encoding/gob/gobencdec_test.go
index 83644c0331..45240d764d 100644
--- a/src/pkg/encoding/gob/gobencdec_test.go
+++ b/src/pkg/encoding/gob/gobencdec_test.go
@@ -573,3 +573,22 @@ func TestGobEncodeIsZero(t *testing.T) {
 		t.Fatalf("%v != %v", x, y)
 	}
 }
+
+func TestGobEncodePtrError(t *testing.T) {
+	var err error
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err = enc.Encode(&err)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	dec := NewDecoder(b)
+	err2 := fmt.Errorf("foo")
+	err = dec.Decode(&err2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if err2 != nil {
+		t.Fatalf("expected nil, got %v", err2)
+	}
+}
-- 
2.50.0