bpo-17288: Prevent jumps from 'return' and 'exception' trace events. (GH-6107)

(cherry picked from commit e32bbaf376)
This commit is contained in:
xdegaye 2018-03-13 18:31:31 +01:00 committed by Serhiy Storchaka
parent 5affd5c29e
commit b8e9d6c5cd
3 changed files with 93 additions and 15 deletions

View File

@ -555,20 +555,35 @@ class RaisingTraceFuncTestCase(unittest.TestCase):
class JumpTracer:
"""Defines a trace function that jumps from one place to another."""
def __init__(self, function, jumpFrom, jumpTo):
self.function = function
def __init__(self, function, jumpFrom, jumpTo, event='line',
decorated=False):
self.code = function.__code__
self.jumpFrom = jumpFrom
self.jumpTo = jumpTo
self.event = event
self.firstLine = None if decorated else self.code.co_firstlineno
self.done = False
def trace(self, frame, event, arg):
if not self.done and frame.f_code == self.function.__code__:
firstLine = frame.f_code.co_firstlineno
if event == 'line' and frame.f_lineno == firstLine + self.jumpFrom:
if self.done:
return
# frame.f_code.co_firstlineno is the first line of the decorator when
# 'function' is decorated and the decorator may be written using
# multiple physical lines when it is too long. Use the first line
# trace event in 'function' to find the first line of 'function'.
if (self.firstLine is None and frame.f_code == self.code and
event == 'line'):
self.firstLine = frame.f_lineno - 1
if (event == self.event and self.firstLine and
frame.f_lineno == self.firstLine + self.jumpFrom):
f = frame
while f is not None and f.f_code != self.code:
f = f.f_back
if f is not None:
# Cope with non-integer self.jumpTo (because of
# no_jump_to_non_integers below).
try:
frame.f_lineno = firstLine + self.jumpTo
frame.f_lineno = self.firstLine + self.jumpTo
except TypeError:
frame.f_lineno = self.jumpTo
self.done = True
@ -608,8 +623,9 @@ class JumpTestCase(unittest.TestCase):
"Expected: " + repr(expected) + "\n" +
"Received: " + repr(received))
def run_test(self, func, jumpFrom, jumpTo, expected, error=None):
tracer = JumpTracer(func, jumpFrom, jumpTo)
def run_test(self, func, jumpFrom, jumpTo, expected, error=None,
event='line', decorated=False):
tracer = JumpTracer(func, jumpFrom, jumpTo, event, decorated)
sys.settrace(tracer.trace)
output = []
if error is None:
@ -620,15 +636,15 @@ class JumpTestCase(unittest.TestCase):
sys.settrace(None)
self.compare_jump_output(expected, output)
def jump_test(jumpFrom, jumpTo, expected, error=None):
def jump_test(jumpFrom, jumpTo, expected, error=None, event='line'):
"""Decorator that creates a test that makes a jump
from one place to another in the following code.
"""
def decorator(func):
@wraps(func)
def test(self):
# +1 to compensate a decorator line
self.run_test(func, jumpFrom+1, jumpTo+1, expected, error)
self.run_test(func, jumpFrom, jumpTo, expected,
error=error, event=event, decorated=True)
return test
return decorator
@ -1128,6 +1144,36 @@ output.append(4)
sys.settrace(None)
self.compare_jump_output([2, 3, 2, 3, 4], namespace["output"])
@jump_test(2, 3, [1], event='call', error=(ValueError, "can't jump from"
" the 'call' trace event of a new frame"))
def test_no_jump_from_call(output):
output.append(1)
def nested():
output.append(3)
nested()
output.append(5)
@jump_test(2, 1, [1], event='return', error=(ValueError,
"can only jump from a 'line' trace event"))
def test_no_jump_from_return_event(output):
output.append(1)
return
@jump_test(2, 1, [1], event='exception', error=(ValueError,
"can only jump from a 'line' trace event"))
def test_no_jump_from_exception_event(output):
output.append(1)
1 / 0
@jump_test(3, 2, [2], event='return', error=(ValueError,
"can't jump from a yield statement"))
def test_no_jump_from_yield(output):
def gen():
output.append(2)
yield 3
next(gen())
output.append(5)
if __name__ == "__main__":
unittest.main()

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@ -0,0 +1 @@
Prevent jumps from 'return' and 'exception' trace events.

View File

@ -81,6 +81,9 @@ get_arg(const _Py_CODEUNIT *codestr, Py_ssize_t i)
* the blockstack needs to be set up before their code runs.
* o 'for' and 'async for' loops can't be jumped into because the
* iterator needs to be on the stack.
* o Jumps cannot be made from within a trace function invoked with a
* 'return' or 'exception' event since the eval loop has been exited at
* that time.
*/
static int
frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
@ -109,13 +112,32 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
return -1;
}
/* Upon the 'call' trace event of a new frame, f->f_lasti is -1 and
* f->f_trace is NULL, check first on the first condition.
* Forbidding jumps from the 'call' event of a new frame is a side effect
* of allowing to set f_lineno only from trace functions. */
if (f->f_lasti == -1) {
PyErr_Format(PyExc_ValueError,
"can't jump from the 'call' trace event of a new frame");
return -1;
}
/* You can only do this from within a trace function, not via
* _getframe or similar hackery. */
if (!f->f_trace)
{
if (!f->f_trace) {
PyErr_Format(PyExc_ValueError,
"f_lineno can only be set by a"
" line trace function");
"f_lineno can only be set by a trace function");
return -1;
}
/* Forbid jumps upon a 'return' trace event (except after executing a
* YIELD_VALUE or YIELD_FROM opcode, f_stacktop is not NULL in that case)
* and upon an 'exception' trace event.
* Jumps from 'call' trace events have already been forbidden above for new
* frames, so this check does not change anything for 'call' events. */
if (f->f_stacktop == NULL) {
PyErr_SetString(PyExc_ValueError,
"can only jump from a 'line' trace event");
return -1;
}
@ -175,6 +197,15 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
/* We're now ready to look at the bytecode. */
PyBytes_AsStringAndSize(f->f_code->co_code, (char **)&code, &code_len);
/* The trace function is called with a 'return' trace event after the
* execution of a yield statement. */
assert(f->f_lasti != -1);
if (code[f->f_lasti] == YIELD_VALUE || code[f->f_lasti] == YIELD_FROM) {
PyErr_SetString(PyExc_ValueError,
"can't jump from a yield statement");
return -1;
}
/* You can't jump onto a line with an 'except' statement on it -
* they expect to have an exception on the top of the stack, which
* won't be true if you jump to them. They always start with code