From ff39b162a6d3bbfc5a9f46097f7d6e7a224fe2fb Mon Sep 17 00:00:00 2001
From: Andy Asp <andy.asp@grafana.com>
Date: Wed, 20 Sep 2023 12:31:49 -0400
Subject: [PATCH 1/2] S3: clone putUserMetadata map to prevent concurrent
 modification

Signed-off-by: Andy Asp <andy.asp@grafana.com>
---
 providers/s3/s3.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/providers/s3/s3.go b/providers/s3/s3.go
index f92d3973..83e3a2de 100644
--- a/providers/s3/s3.go
+++ b/providers/s3/s3.go
@@ -492,6 +492,13 @@ func (b *Bucket) Upload(ctx context.Context, name string, r io.Reader) error {
 	if size < int64(partSize) {
 		partSize = 0
 	}
+
+	// Cloning map since minio may modify it
+	userMetadata := make(map[string]string, len(b.putUserMetadata))
+	for k, v := range b.putUserMetadata {
+		userMetadata[k] = v
+	}
+
 	if _, err := b.client.PutObject(
 		ctx,
 		b.name,
@@ -501,7 +508,7 @@ func (b *Bucket) Upload(ctx context.Context, name string, r io.Reader) error {
 		minio.PutObjectOptions{
 			PartSize:             partSize,
 			ServerSideEncryption: sse,
-			UserMetadata:         b.putUserMetadata,
+			UserMetadata:         userMetadata,
 			StorageClass:         b.storageClass,
 			// 4 is what minio-go have as the default. To be certain we do micro benchmark before any changes we
 			// ensure we pin this number to four.

From a557e75bcb9ea67a663b6329571b5a1d0794969c Mon Sep 17 00:00:00 2001
From: Andy Asp <andy.asp@grafana.com>
Date: Wed, 20 Sep 2023 14:16:35 -0400
Subject: [PATCH 2/2] Add changelog entry

Signed-off-by: Andy Asp <andy.asp@grafana.com>
---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e26b1548..0dc65033 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#34](https://github.com/thanos-io/objstore/pull/34) Fix ignored options when creating shared credential Azure client.
 - [#62](https://github.com/thanos-io/objstore/pull/62) S3: Fix ignored context cancellation in `Iter` method.
 - [#77](https://github.com/thanos-io/objstore/pull/77) Fix buckets wrapped with metrics from being unable to determine object sizes in `Upload`.
+- [#78](https://github.com/thanos-io/objstore/pull/78) S3: Fix possible concurrent modification of the PutUserMetadata map.
 
 ### Added
 - [#15](https://github.com/thanos-io/objstore/pull/15) Add Oracle Cloud Infrastructure Object Storage Bucket support.