fix: prevent nil deref when reading in-memory tables

table/table.go

@@ -553,7 +553,7 @@ func (t *Table) block(idx int, useCache bool) (*Block, error) {
 	if blk.data, err = t.read(blk.offset, int(ko.Len())); err != nil {
 		return nil, y.Wrapf(err,
 			"failed to read from file: %s at offset: %d, len: %d",
-			t.Fd.Name(), blk.offset, ko.Len())
+			t.Filename(), blk.offset, ko.Len())
 	}
 
 	if t.shouldDecrypt() {
@@ -568,7 +568,7 @@ func (t *Table) block(idx int, useCache bool) (*Block, error) {
 	if err = t.decompress(blk); err != nil {
 		return nil, y.Wrapf(err,
 			"failed to decode compressed data in file: %s at offset: %d, len: %d",
-			t.Fd.Name(), blk.offset, ko.Len())
+			t.Filename(), blk.offset, ko.Len())
 	}
 
 	// Read meta data related to block.
@@ -659,7 +659,12 @@ func (t *Table) Smallest() []byte { return t.smallest }
 func (t *Table) Biggest() []byte { return t.biggest }
 
 // Filename is NOT the file name.  Just kidding, it is.
-func (t *Table) Filename() string { return t.Fd.Name() }
+func (t *Table) Filename() string {
+	if t.Fd == nil {
+		return IDToFilename(t.id)
+	}
+	return t.Fd.Name()
+}
 
 // ID is the table's ID number (used to make the file name).
 func (t *Table) ID() uint64 { return t.id }

table/table_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/dgraph-io/badger/v4/options"
 	"github.com/dgraph-io/badger/v4/y"
 	"github.com/dgraph-io/ristretto/v2"
+	"github.com/dgraph-io/ristretto/v2/z"
 )
 
 func key(prefix string, i int) string {
@@ -896,3 +897,39 @@ func TestMaxVersion(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, N, int(table.MaxVersion()))
 }
+
+func TestInMemoryTableBlockErrorNoPanic(t *testing.T) {
+	opts := getTestTableOptions()
+	src := buildTestTable(t, "key", 500, opts)
+
+	data := make([]byte, len(src.Data))
+	copy(data, src.Data)
+	srcID := src.ID()
+	require.NoError(t, src.DecrRef())
+
+	tbl, err := OpenInMemoryTable(data, srcID, &opts)
+	require.NoError(t, err)
+	defer func() { require.NoError(t, tbl.DecrRef()) }()
+
+	corruptEnd := tbl.indexStart
+	if corruptEnd > 256 {
+		corruptEnd = 256
+	}
+	for i := 0; i < corruptEnd; i++ {
+		data[i] = 0xFF
+	}
+
+	require.NotPanics(t, func() {
+		_, err = tbl.block(0, false)
+	})
+	require.Error(t, err)
+}
+
+func TestInMemoryTableFilename(t *testing.T) {
+	tbl := &Table{
+		MmapFile: &z.MmapFile{Data: []byte{}, Fd: nil},
+		id:       777,
+		opt:      &Options{},
+	}
+	require.Equal(t, IDToFilename(777), tbl.Filename())
+}