QUERY · ISSUE
uctypes.bytearray_at() accepts negative address and segfaults on write
bugproposed-close
Port, board and/or hardware
Unix port
MicroPython version
MicroPython v1.27.0-preview.107.gd1607598f on 2025-09-09; linux [GCC 14.2.0] version
Reproduction
try:
import uctypes
except ImportError:
print("SKIP missing uctypes")
else:
try:
ba = uctypes.bytearray_at(-9223372036854775808, 4) # -2**63
ba[0] = 1 # write to the mapped memory
print('should not reach here')
except Exception as e:
print("EXC %s" % type(e).__name__)
Expected behaviour
A Python-level exception instead of process crash, e.g.:
-
ValueError/OverflowError for negative address; or
-
OSError if the address is not accessible.
At minimum, uctypes.bytearray_at() should reject negative addresses on 64-bit builds rather than silently converting them to huge unsigned pointers.
Observed behaviour
Program received signal SIGSEGV, Segmentation fault.
#0 mp_binary_set_val_array_from_int(typecode=0x1, p=0x8000000000000000, index=0x0, val=0x1)
#1 mp_binary_set_val_array(...)
#2 array_subscr(...)
#3 mp_obj_subscr(...)
#4 mp_execute_bytecode(...)
Additional Information
No, I've provided everything above.
Code of Conduct
Yes, I agree
CANDIDATE · ISSUE
uctypes.bytes_at() accepts out-of-range (non-canonical) address and segfaults
bug
Port, board and/or hardware
Unix port
MicroPython version
MicroPython v1.27.0-preview.107.gd1607598f on 2025-09-09; linux [GCC 14.2.0] version
Reproduction
A Python-level exception when the address is obviously invalid, e.g.:
- ValueError/OverflowError for negative/out-of-range addresses, or
- OSError if the runtime chooses to probe and detect unreadable memory on the unix port.
At minimum, reject negative addresses and detect addr + size overflow to avoid trivial VM crashes.
Expected behaviour
import uctypes
ptr = 1 << 48
arr = uctypes.bytes_at(ptr, 8)
print('READ', arr)
Observed behaviour
Program received signal SIGSEGV, Segmentation fault.
#0 qstr_compute_hash(data=0x1000000000000, len=0x8)
#1 mp_obj_new_str_copy(type=mp_type_bytes, data=0x1000000000000, len=0x8)
#2 mp_obj_new_bytes(...)
#3 uctypes_struct_bytes_at(ptr=0x1000000000000, size=0x8)
#4 fun_builtin_2_call(...)
#5 mp_call_function_n_kw(...)
#6 mp_execute_bytecode(...)
...
Additional Information
No, I've provided everything above.
Code of Conduct
Yes, I agree