execfile: segmentation fault with incorrect Python vfs implementation #17841
Description
Port, board and/or hardware
unix port, coverage build, x86_64
MicroPython version
MicroPython v1.26.0-preview.524.g255d74b5a8.dirty on 2025-08-05; linux [GCC 12.2.0] version
Reproduction
Use the following script.
import os
import vfs
class Filesystem:
def mount(self, readonly, mkfs):
pass
def open(self, file, mode):
return None # violates vfs contract
fs = Filesystem()
vfs.mount(fs, "/test_mnt")
execfile("/test_mnt/test.py")Expected behaviour
Prints a Python exception because the return type from open() is incorrect (not a VFS file)
Observed behaviour
Crashes with a segmentation fault
Additional Information
gdb says:
Program received signal SIGSEGV, Segmentation fault.
mp_reader_new_file (reader=reader@entry=0x7fffffffd820,
filename=filename@entry=876) at ../../extmod/vfs_reader.c:86
86 const mp_stream_p_t *stream_p = mp_get_stream(file);
(gdb) where
#0 mp_reader_new_file (reader=reader@entry=0x7fffffffd820,
filename=filename@entry=876) at ../../extmod/vfs_reader.c:86
#1 0x00005555555c4ca3 in mp_lexer_new_from_file (filename=876)
at ../../py/lexer.c:897
#2 0x000055555561b5bf in eval_exec_helper (n_args=1, args=0x7fffffffda50,
parse_input_kind=parse_input_kind@entry=MP_PARSE_SINGLE_INPUT)
at ../../py/builtinevex.c:167
#3 0x000055555561b782 in mp_builtin_execfile (n_args=<optimized out>,
args=<optimized out>) at ../../py/builtinevex.c:195
possibly mp_get_stream_raise should be used instead?
Code of Conduct
Yes, I agree