Check string indices when loading binary chunk

Lua is not religious about that, but it tries to avoid crashes when
loading binary chunks.

lundump.c

@@ -154,8 +154,9 @@ static void loadString (LoadState *S, Proto *p, TString **sl) {
   else if (size == 1) {  /* previously saved string? */
     lua_Unsigned idx = loadVarint(S, LUA_MAXUNSIGNED);  /* get its index */
     TValue stv;
-    luaH_getint(S->h, l_castU2S(idx), &stv);  /* get its value */
-    *sl = ts = tsvalue(&stv);
+    if (novariant(luaH_getint(S->h, l_castU2S(idx), &stv)) != LUA_TSTRING)
+      error(S, "invalid string index");
+    *sl = ts = tsvalue(&stv);  /* get its value */
     luaC_objbarrier(L, p, ts);
     return;  /* do not save it again */
   }
@@ -394,11 +395,10 @@ LClosure *luaU_undump (lua_State *L, ZIO *Z, const char *name, int fixed) {
   LoadState S;
   LClosure *cl;
   if (*name == '@' || *name == '=')
-    S.name = name + 1;
+    name = name + 1;
   else if (*name == LUA_SIGNATURE[0])
-    S.name = "binary string";
-  else
-    S.name = name;
+    name = "binary string";
+  S.name = name;
   S.L = L;
   S.Z = Z;
   S.fixed = cast_byte(fixed);

manual/manual.of

@@ -1403,8 +1403,7 @@ see the program @idx{luac} and the function @Lid{string.dump} for details.
 Programs in source and compiled forms are interchangeable;
 Lua automatically detects the file type and acts accordingly @seeF{load}.
 Be aware that, unlike source code,
-the execution of maliciously crafted
-bytecode can crash the interpreter.
+maliciously crafted binary chunks can crash the interpreter.
 
 }
 
@@ -6694,11 +6693,10 @@ It may be the string @St{b} (only @x{binary chunk}s),
 or @St{bt} (both binary and text).
 The default is @St{bt}.
 
-It is safe to load malformed binary chunks;
-@id{load} signals an appropriate error.
-However,
-Lua does not check the consistency of the code inside binary chunks;
-running maliciously crafted bytecode can crash the interpreter.
+Lua does not check the consistency of binary chunks.
+Maliciously crafted binary chunks can crash
+the interpreter.
+You can use the @id{mode} parameter to prevent loading binary chunks.
 
 }