bpo-36851: Clean the frame stack if the execution ends with a return and the stack is not empty (GH-13191)

This commit is contained in:
Pablo Galindo 2019-05-09 16:52:02 +01:00 committed by GitHub
parent 33e067d6a2
commit f00828a742
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 49 additions and 7 deletions

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@ -130,6 +130,7 @@ import sys
import threading
import unittest
import weakref
import opcode
try:
import ctypes
except ImportError:
@ -379,6 +380,43 @@ if check_impl_detail(cpython=True) and ctypes is not None:
tt.join()
self.assertEqual(LAST_FREED, 500)
@cpython_only
def test_clean_stack_on_return(self):
def f(x):
return x
code = f.__code__
ct = type(f.__code__)
# Insert an extra LOAD_FAST, this duplicates the value of
# 'x' in the stack, leaking it if the frame is not properly
# cleaned up upon exit.
bytecode = list(code.co_code)
bytecode.insert(-2, opcode.opmap['LOAD_FAST'])
bytecode.insert(-2, 0)
c = ct(code.co_argcount, code.co_posonlyargcount,
code.co_kwonlyargcount, code.co_nlocals, code.co_stacksize+1,
code.co_flags, bytes(bytecode),
code.co_consts, code.co_names, code.co_varnames,
code.co_filename, code.co_name, code.co_firstlineno,
code.co_lnotab, code.co_freevars, code.co_cellvars)
new_function = type(f)(c, f.__globals__, 'nf', f.__defaults__, f.__closure__)
class Var:
pass
the_object = Var()
var = weakref.ref(the_object)
new_function(the_object)
# Check if the_object is leaked
del the_object
assert var() is None
def test_main(verbose=None):
from test import test_code
run_doctest(test_code, verbose)

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@ -0,0 +1,2 @@
The ``FrameType`` stack is now correctly cleaned up if the execution ends
with a return and the stack is not empty.

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@ -1755,7 +1755,7 @@ main_loop:
case TARGET(RETURN_VALUE): {
retval = POP();
assert(f->f_iblock == 0);
goto return_or_yield;
goto exit_returning;
}
case TARGET(GET_AITER): {
@ -1924,7 +1924,7 @@ main_loop:
/* and repeat... */
assert(f->f_lasti >= (int)sizeof(_Py_CODEUNIT));
f->f_lasti -= sizeof(_Py_CODEUNIT);
goto return_or_yield;
goto exit_yielding;
}
case TARGET(YIELD_VALUE): {
@ -1941,7 +1941,7 @@ main_loop:
}
f->f_stacktop = stack_pointer;
goto return_or_yield;
goto exit_yielding;
}
case TARGET(POP_EXCEPT): {
@ -3581,16 +3581,18 @@ exception_unwind:
break;
} /* main loop */
assert(retval == NULL);
assert(PyErr_Occurred());
exit_returning:
/* Pop remaining stack entries. */
while (!EMPTY()) {
PyObject *o = POP();
Py_XDECREF(o);
}
assert(retval == NULL);
assert(PyErr_Occurred());
return_or_yield:
exit_yielding:
if (tstate->use_tracing) {
if (tstate->c_tracefunc) {
if (call_trace_protected(tstate->c_tracefunc, tstate->c_traceobj,