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

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(cherry picked from commit e32bbaf376)
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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
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39
Objects/frameobject.c
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@ -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