Validates label matchers in the querier (grafana/phlare#601)

pkg/querier/querier.go

@@ -18,6 +18,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/common/model"
+	"github.com/prometheus/prometheus/promql/parser"
 	"github.com/samber/lo"
 	"golang.org/x/sync/errgroup"
 
@@ -224,6 +225,10 @@ func (q *Querier) SelectMergeStacktraces(ctx context.Context, req *connect.Reque
 	if err != nil {
 		return nil, connect.NewError(connect.CodeInvalidArgument, err)
 	}
+	_, err = parser.ParseMetricSelector(req.Msg.LabelSelector)
+	if err != nil {
+		return nil, connect.NewError(connect.CodeInvalidArgument, err)
+	}
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
@@ -280,6 +285,10 @@ func (q *Querier) SelectMergeProfile(ctx context.Context, req *connect.Request[q
 	if err != nil {
 		return nil, connect.NewError(connect.CodeInvalidArgument, err)
 	}
+	_, err = parser.ParseMetricSelector(req.Msg.LabelSelector)
+	if err != nil {
+		return nil, connect.NewError(connect.CodeInvalidArgument, err)
+	}
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
@@ -338,6 +347,11 @@ func (q *Querier) SelectSeries(ctx context.Context, req *connect.Request[querier
 		return nil, connect.NewError(connect.CodeInvalidArgument, err)
 	}
 
+	_, err = parser.ParseMetricSelector(req.Msg.LabelSelector)
+	if err != nil {
+		return nil, connect.NewError(connect.CodeInvalidArgument, err)
+	}
+
 	if req.Msg.Start > req.Msg.End {
 		return nil, connect.NewError(connect.CodeInvalidArgument, errors.New("start must be before end"))
 	}