Merge pull request #78 from andyasp/clone-putUserMetadata

S3: clone putUserMetadata map to prevent concurrent modification

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.

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.