remotes: fix possible panic from WithMediaTypeKeyPrefix

tonistiigi · k8s-infra-cherrypick-robot · commit 8b73c2de310e · 2025-11-14T20:49:44.000Z
As the same instance of a map is used in context and mutated
directly, this leads to a  situation where:
- Calling WithMediaTypeKeyPrefix from parallel goroutines where
  the context was based on the same base context can trigger a panic.
- A subcontext calling WithMediaTypeKeyPrefix changes the value for
  another context when they both originate from the same base context.

Signed-off-by: Tonis Tiigi &lt;tonistiigi@gmail.com&gt;
diff --git a/core/remotes/handlers.go b/core/remotes/handlers.go
@@ -22,6 +22,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"maps"
 	"strings"
 	"sync"
 
@@ -45,6 +46,7 @@ func WithMediaTypeKeyPrefix(ctx context.Context, mediaType, prefix string) conte
 	var values map[string]string
 	if v := ctx.Value(refKeyPrefix{}); v != nil {
 		values = v.(map[string]string)
+		values = maps.Clone(values)
 	} else {
 		values = make(map[string]string)
 	}
