debug/macho: don't crash if dynamic symtab with no symtab

No test case because the problem can only happen for invalid data. Let the fuzzer find cases like this. For #47653 Fixes #58642 Change-Id: I19fee0dc9bd6239b520c15182b8f1e57bb0049bb Reviewed-on: https://go-review.googlesource.com/c/go/+/470397 Reviewed-by: Ian Lance Taylor <[email protected]> Run-TryBot: Ian Lance Taylor <[email protected]> Auto-Submit: Ian Lance Taylor <[email protected]> Run-TryBot: Ian Lance Taylor <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Bryan Mills <[email protected]>
golang · Feb 22, 2023 · e7cfcda · e7cfcda
1 parent 06b6759
commit e7cfcda
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/debug/macho/file.go b/src/debug/macho/file.go
@@ -350,7 +350,9 @@ func NewFile(r io.ReaderAt) (*File, error) {
 			if err := binary.Read(b, bo, &hdr); err != nil {
 				return nil, err
 			}
-			if hdr.Iundefsym > uint32(len(f.Symtab.Syms)) {
+			if f.Symtab == nil {
+				return nil, &FormatError{offset, "dynamic symbol table seen before any ordinary symbol table", nil}
+			} else if hdr.Iundefsym > uint32(len(f.Symtab.Syms)) {
 				return nil, &FormatError{offset, fmt.Sprintf(
 					"undefined symbols index in dynamic symbol table command is greater than symbol table length (%d > %d)",
 					hdr.Iundefsym, len(f.Symtab.Syms)), nil}