py/builtinevex: Handle invalid filenames for execfile.

If a non-string buffer was passed to execfile, then it would be passed
as a non-null-terminated char* to mp_lexer_new_from_file.

This changes mp_lexer_new_from_file to take a qstr instead (as in almost
all cases a qstr will be created from this input anyway to set the
`__file__` attribute on the module).

This now makes execfile require a string (not generic buffer) argument,
which is probably a good fix to make anyway.

Fixes issue #12522.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/py/builtinevex.c b/py/builtinevex.c
index 97eab7fad..73fca5d39 100644
--- a/py/builtinevex.c
+++ b/py/builtinevex.c
@@ -136,17 +136,18 @@ STATIC mp_obj_t eval_exec_helper(size_t n_args, const mp_obj_t *args, mp_parse_i
     }
     #endif
 
-    // Extract the source code.
-    mp_buffer_info_t bufinfo;
-    mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);
 
     // create the lexer
     // MP_PARSE_SINGLE_INPUT is used to indicate a file input
     mp_lexer_t *lex;
     if (MICROPY_PY_BUILTINS_EXECFILE && parse_input_kind == MP_PARSE_SINGLE_INPUT) {
-        lex = mp_lexer_new_from_file(bufinfo.buf);
+        lex = mp_lexer_new_from_file(mp_obj_str_get_qstr(args[0]));
         parse_input_kind = MP_PARSE_FILE_INPUT;
     } else {
+        // Extract the source code.
+        mp_buffer_info_t bufinfo;
+        mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);
+
         lex = mp_lexer_new_from_str_len(MP_QSTR__lt_string_gt_, bufinfo.buf, bufinfo.len, 0);
     }