Store: Fix panic too smaller buffer (#7658)

Co-authored-by: dominic.qi <dominic.qi@jaco.live>
Co-authored-by: Ben Ye <benye@amazon.com>

CHANGELOG.md

@@ -16,6 +16,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#7592](https://github.com/thanos-io/thanos/pull/7592) Ruler: Only increment `thanos_rule_evaluation_with_warnings_total` metric for non PromQL warnings.
 - [#7614](https://github.com/thanos-io/thanos/pull/7614) *: fix debug log formatting.
 - [#7492](https://github.com/thanos-io/thanos/pull/7492) Compactor: update filtered blocks list before second downsample pass.
+- [#7658](https://github.com/thanos-io/thanos/pull/7658) Store: Fix panic because too small buffer in pool.
 - [#7643](https://github.com/thanos-io/thanos/pull/7643) Receive: fix thanos_receive_write_{timeseries,samples} stats
 - [#7644](https://github.com/thanos-io/thanos/pull/7644) fix(ui): add null check to find overlapping blocks logic
 - [#7679](https://github.com/thanos-io/thanos/pull/7679) Query: respect store.limit.* flags when evaluating queries

pkg/store/bucket.go

@@ -3605,10 +3605,10 @@ func (r *bucketChunkReader) loadChunks(ctx context.Context, res []seriesEntry, a
 	bufPooled, err := r.block.chunkPool.Get(r.block.estimatedMaxChunkSize)
 	if err == nil {
 		buf = *bufPooled
+		defer r.block.chunkPool.Put(&buf)
 	} else {
 		buf = make([]byte, r.block.estimatedMaxChunkSize)
 	}
-	defer r.block.chunkPool.Put(&buf)
 
 	for i, pIdx := range pIdxs {
 		// Fast forward range reader to the next chunk start in case of sparse (for our purposes) byte range.