[2.7] bpo-17288: Prevent jumps from 'return' and 'exception' trace events. (GH-6111)
(cherry picked from commit e32bbaf376a09c149fa7c7f2919d7c9ce4e2a055)
diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
index 04b1ac3..d8737af 100644
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -482,20 +482,35 @@
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.func_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.func_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
@@ -535,8 +550,9 @@
"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:
@@ -547,15 +563,15 @@
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
@@ -1018,6 +1034,36 @@
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)
+
def test_main():
test_support.run_unittest(
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-02-27-13-36-21.bpo-17288.Gdj24S.rst b/Misc/NEWS.d/next/Core and Builtins/2018-02-27-13-36-21.bpo-17288.Gdj24S.rst
new file mode 100644
index 0000000..ce9e84c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-02-27-13-36-21.bpo-17288.Gdj24S.rst
@@ -0,0 +1 @@
+Prevent jumps from 'return' and 'exception' trace events.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index bf1c7c5..1758745 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -89,6 +89,9 @@
* o 'try'/'for'/'while' blocks can't be jumped into because the blockstack
* needs to be set up before their code runs, and for 'for' loops 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)
@@ -122,13 +125,32 @@
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 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;
}
@@ -178,6 +200,15 @@
min_addr = MIN(new_lasti, f->f_lasti);
max_addr = MAX(new_lasti, f->f_lasti);
+ /* 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) {
+ 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