From b042e29569eb99d57e3175e05cb16330160637ae Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@grafana.com>
Date: Thu, 16 Dec 2021 12:01:54 +0100
Subject: [PATCH 1/2] storage: expose bug in iterators #10027

Signed-off-by: beorn7 <beorn@grafana.com>
---
 storage/remote/codec_test.go | 5 +++++
 storage/series_test.go       | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/storage/remote/codec_test.go b/storage/remote/codec_test.go
index 1432736e13..be52bd312e 100644
--- a/storage/remote/codec_test.go
+++ b/storage/remote/codec_test.go
@@ -233,6 +233,11 @@ func TestConcreteSeriesIterator(t *testing.T) {
 	ts, v = it.At()
 	require.Equal(t, int64(3), ts)
 	require.Equal(t, 3., v)
+
+	// Seek beyond the end.
+	require.False(t, it.Seek(5))
+	// And we don't go back. (This exposes issue #10027.)
+	require.False(t, it.Seek(2))
 }
 
 func TestFromQueryResultWithDuplicates(t *testing.T) {
diff --git a/storage/series_test.go b/storage/series_test.go
index 384009de43..8ce4a7222f 100644
--- a/storage/series_test.go
+++ b/storage/series_test.go
@@ -51,4 +51,9 @@ func TestListSeriesIterator(t *testing.T) {
 	ts, v = it.At()
 	require.Equal(t, int64(3), ts)
 	require.Equal(t, 3., v)
+
+	// Seek beyond the end.
+	require.False(t, it.Seek(5))
+	// And we don't go back. (This exposes issue #10027.)
+	require.False(t, it.Seek(2))
 }

From 0ede6ae321be76db1567e29676776382ea60a543 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@grafana.com>
Date: Thu, 16 Dec 2021 12:07:07 +0100
Subject: [PATCH 2/2] storage: fix bug #10027 in iterators' Seek method

Signed-off-by: beorn7 <beorn@grafana.com>
---
 storage/remote/codec.go      | 3 +++
 storage/series.go            | 3 +++
 tsdb/tsdbutil/buffer_test.go | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/storage/remote/codec.go b/storage/remote/codec.go
index fa033b5895..fb4d777a34 100644
--- a/storage/remote/codec.go
+++ b/storage/remote/codec.go
@@ -360,6 +360,9 @@ func (c *concreteSeriesIterator) Seek(t int64) bool {
 	if c.cur == -1 {
 		c.cur = 0
 	}
+	if c.cur >= len(c.series.samples) {
+		return false
+	}
 	// No-op check.
 	if s := c.series.samples[c.cur]; s.Timestamp >= t {
 		return true
diff --git a/storage/series.go b/storage/series.go
index 024b0fc72f..2dba837156 100644
--- a/storage/series.go
+++ b/storage/series.go
@@ -99,6 +99,9 @@ func (it *listSeriesIterator) Seek(t int64) bool {
 	if it.idx == -1 {
 		it.idx = 0
 	}
+	if it.idx >= it.samples.Len() {
+		return false
+	}
 	// No-op check.
 	if s := it.samples.Get(it.idx); s.T() >= t {
 		return true
diff --git a/tsdb/tsdbutil/buffer_test.go b/tsdb/tsdbutil/buffer_test.go
index baae8266bb..f194033607 100644
--- a/tsdb/tsdbutil/buffer_test.go
+++ b/tsdb/tsdbutil/buffer_test.go
@@ -159,6 +159,9 @@ func (it *listSeriesIterator) Seek(t int64) bool {
 	if it.idx == -1 {
 		it.idx = 0
 	}
+	if it.idx >= len(it.list) {
+		return false
+	}
 	// No-op check.
 	if s := it.list[it.idx]; s.T() >= t {
 		return true