backupinfo: fix error handling in desciter

Previously, the DescIter.Valid would return (false, nil) if the
underlying SST iterator was in an error state. This is an "empty" state
when it needs to propagate the error.

Fixes: #151144
Release note: Fixes a rare bug in restore where an object storage on
restore start could cause restore to report success without creating the
restored tables or databases.

Author: jeffswenson

pkg/backup/backupinfo/BUILD.bazel

@@ -58,11 +58,12 @@ go_library(
 go_test(
     name = "backupinfo_test",
     srcs = [
+        "desc_sst_test.go",
         "main_test.go",
         "manifest_handling_test.go",
     ],
+    embed = [":backupinfo"],
     deps = [
-        ":backupinfo",
         "//pkg/backup/backuppb",
         "//pkg/base",
         "//pkg/blobs",
@@ -86,6 +87,7 @@ go_test(
         "//pkg/util/leaktest",
         "//pkg/util/log",
         "//pkg/util/randutil",
+        "@com_github_cockroachdb_errors//:errors",
         "@com_github_stretchr_testify//require",
     ],
 )

pkg/backup/backupinfo/desc_sst.go

@@ -303,6 +303,10 @@ func (di *DescIterator) Next() {
 			break
 		}
 	}
+	if di.backing.iterError != nil {
+		di.err = di.backing.iterError
+		return
+	}
 
 	di.value = nextValue
 }

pkg/backup/backupinfo/desc_sst_test.go

@@ -0,0 +1,32 @@
+// Copyright 2025 The Cockroach Authors.
+//
+// Use of this software is governed by the CockroachDB Software License
+// included in the /LICENSE file.
+
+package backupinfo
+
+import (
+	"testing"
+
+	"github.com/cockroachdb/cockroach/pkg/util/leaktest"
+	"github.com/cockroachdb/cockroach/pkg/util/log"
+	"github.com/cockroachdb/errors"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDescSSTError(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+	defer log.Scope(t).Close(t)
+
+	iter := &DescIterator{
+		backing: bytesIter{
+			iterError: errors.New("internal iterator error"),
+		},
+	}
+
+	iter.Next()
+
+	valid, err := iter.Valid()
+	require.False(t, valid)
+	require.Error(t, err)
+}