From 2e28e1215ab8cf48cee837b88426589cab7d38b9 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Wed, 9 Feb 2022 12:27:36 +0800
Subject: [PATCH] ddl, util/codec: fix add index OOM and prevent panic in
 logging (#29925) (#30123)

close pingcap/tidb#27687
---
 ddl/backfilling.go            |  7 +++++++
 tablecodec/tablecodec_test.go | 14 ++++++++++++++
 util/codec/codec.go           |  4 +++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/ddl/backfilling.go b/ddl/backfilling.go
index 8a5b7a837f552..c6f1b28c42f22 100644
--- a/ddl/backfilling.go
+++ b/ddl/backfilling.go
@@ -423,6 +423,13 @@ func (w *worker) handleReorgTasks(reorgInfo *reorgInfo, totalAddedCount *int64,
 }
 
 func tryDecodeToHandleString(key kv.Key) string {
+	defer func() {
+		if r := recover(); r != nil {
+			logutil.BgLogger().Warn("tryDecodeToHandleString panic",
+				zap.Any("recover()", r),
+				zap.Binary("key", key))
+		}
+	}()
 	handle, err := tablecodec.DecodeRowKey(key)
 	if err != nil {
 		recordPrefixIdx := bytes.Index(key, []byte("_r"))
diff --git a/tablecodec/tablecodec_test.go b/tablecodec/tablecodec_test.go
index ada284edc0bca..cf461438cf82b 100644
--- a/tablecodec/tablecodec_test.go
+++ b/tablecodec/tablecodec_test.go
@@ -54,6 +54,20 @@ func (s *testTableCodecSuite) TestTableCodec(c *C) {
 	c.Assert(h.IntValue(), Equals, int64(2))
 }
 
+// https://github.com/pingcap/tidb/issues/27687.
+func (s *testTableCodecSuite) TestTableCodecInvalid(c *C) {
+	tableID := int64(100)
+	buf := make([]byte, 0, 11)
+	buf = append(buf, 't')
+	buf = codec.EncodeInt(buf, tableID)
+	buf = append(buf, '_', 'r')
+	buf = codec.EncodeInt(buf, -9078412423848787968)
+	buf = append(buf, '0')
+	_, err := DecodeRowKey(buf)
+	c.Assert(err, NotNil)
+	c.Assert(err.Error(), Equals, "invalid encoded key")
+}
+
 // column is a structure used for test
 type column struct {
 	id int64
diff --git a/util/codec/codec.go b/util/codec/codec.go
index 08ce5a527b192..4d16470d56537 100644
--- a/util/codec/codec.go
+++ b/util/codec/codec.go
@@ -961,7 +961,9 @@ func peek(b []byte) (length int, err error) {
 		return 0, errors.Trace(err)
 	}
 	length += l
-	if length > originLength {
+	if length <= 0 {
+		return 0, errors.New("invalid encoded key")
+	} else if length > originLength {
 		return 0, errors.Errorf("invalid encoded key, "+
 			"expected length: %d, actual length: %d", length, originLength)
 	}