[release-branch.go1.17] encoding/xml: use iterative Skip, rather than recursive

Prevents exhausting the stack limit in _incredibly_ deeply nested
structures.

Fixes #53711
Updates #53614
Fixes CVE-2022-28131

Change-Id: I47db4595ce10cecc29fbd06afce7b299868599e6
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1419912
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
(cherry picked from commit 9278cb78443d2b4deb24cbb5b61c9ba5ac688d49)
Reviewed-on: https://go-review.googlesource.com/c/go/+/417068
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/encoding/xml/read_test.go b/src/encoding/xml/read_test.go
index 8c2e70fa22..4ccab3d010 100644
--- a/src/encoding/xml/read_test.go
+++ b/src/encoding/xml/read_test.go
@@ -5,8 +5,10 @@
 package xml
 
 import (
+	"bytes"
 	"io"
 	"reflect"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -1079,3 +1081,19 @@ func TestUnmarshalWhitespaceAttrs(t *testing.T) {
 		t.Fatalf("whitespace attrs: Unmarshal:\nhave: %#+v\nwant: %#+v", v, want)
 	}
 }
+
+func TestCVE202230633(t *testing.T) {
+	if runtime.GOARCH == "wasm" {
+		t.Skip("causes memory exhaustion on js/wasm")
+	}
+	defer func() {
+		p := recover()
+		if p != nil {
+			t.Fatal("Unmarshal panicked")
+		}
+	}()
+	var example struct {
+		Things []string
+	}
+	Unmarshal(bytes.Repeat([]byte("<a>"), 17_000_000), &example)
+}