filer leveldb2: saturate size options instead of overflowing int

The option fields take int, so a MiB config value past math.MaxInt/MiB
(e.g. 2048 on 32-bit) wrapped negative and goleveldb would panic sizing
the memtable. Clamp the product instead of the input.

weed/filer/leveldb2/leveldb2_store.go

@@ -6,6 +6,7 @@ import (
 	"crypto/md5"
 	"fmt"
 	"io"
+	"math"
 	"os"
 
 	"github.com/syndtr/goleveldb/leveldb"
@@ -56,20 +57,29 @@ func (store *LevelDB2Store) buildOptions() *opt.Options {
 		ReadOnly:           store.ReadOnly,
 	}
 	if store.blockCacheSizeMB > 0 {
-		opts.BlockCacheCapacity = store.blockCacheSizeMB * 1024 * 1024
+		opts.BlockCacheCapacity = scaled(store.blockCacheSizeMB, 1<<20)
 	}
 	if store.writeBufferSizeMB > 0 {
-		opts.WriteBuffer = store.writeBufferSizeMB * 1024 * 1024
+		opts.WriteBuffer = scaled(store.writeBufferSizeMB, 1<<20)
 	}
 	if store.blockSizeKB > 0 {
-		opts.BlockSize = store.blockSizeKB * 1024
+		opts.BlockSize = scaled(store.blockSizeKB, 1<<10)
 	}
 	if store.compactionTableSizeMB > 0 {
-		opts.CompactionTableSize = store.compactionTableSizeMB * 1024 * 1024
+		opts.CompactionTableSize = scaled(store.compactionTableSizeMB, 1<<20)
 	}
 	return opts
 }
 
+// scaled converts a size option to bytes, saturating instead of wrapping a
+// huge value into a negative int on 32-bit builds.
+func scaled(v, scale int) int {
+	if v > math.MaxInt/scale {
+		return math.MaxInt
+	}
+	return v * scale
+}
+
 func (store *LevelDB2Store) initialize(dir string, dbCount int) (err error) {
 	glog.Infof("filer store leveldb2 dir: %s", dir)
 	os.MkdirAll(dir, 0755)

weed/filer/leveldb2/leveldb2_store_test.go

@@ -2,6 +2,7 @@ package leveldb
 
 import (
 	"context"
+	"math"
 	"testing"
 
 	"github.com/seaweedfs/seaweedfs/weed/filer"
@@ -138,6 +139,18 @@ func TestInitializeDefaultOptions(t *testing.T) {
 	}
 }
 
+func TestScaledSaturates(t *testing.T) {
+	if got := scaled(math.MaxInt, 1<<20); got != math.MaxInt {
+		t.Errorf("expected saturation at %d, got %d", math.MaxInt, got)
+	}
+	if got := scaled(64, 1<<20); got != 64*1024*1024 {
+		t.Errorf("expected 64MiB, got %d", got)
+	}
+	if got := scaled(4, 1<<10); got != 4*1024 {
+		t.Errorf("expected 4KiB, got %d", got)
+	}
+}
+
 func TestEmptyRoot(t *testing.T) {
 	testFiler := filer.NewFiler(pb.ServerDiscovery{}, nil, "", "", "", "", "", 255, nil)
 	dir := t.TempDir()