[Python-checkins] bpo-44449: faulthandler don't modify frame refcnt (GH-27850)
miss-islington
webhook-mailer at python.org
Mon Aug 30 09:56:11 EDT 2021
https://github.com/python/cpython/commit/720aef48b558e68c07937f0cc8d62a60f23dcb3d
commit: 720aef48b558e68c07937f0cc8d62a60f23dcb3d
branch: 3.9
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2021-08-30T06:56:03-07:00
summary:
bpo-44449: faulthandler don't modify frame refcnt (GH-27850)
Fix a crash in the signal handler of the faulthandler module: no
longer modify the reference count of frame objects.
(cherry picked from commit fe997e1a67835a929705c8c305d41c4d7dd326e3)
Co-authored-by: Victor Stinner <vstinner at python.org>
files:
A Misc/NEWS.d/next/Library/2021-08-20-11-30-52.bpo-44449.1r2-lS.rst
M Python/traceback.c
diff --git a/Misc/NEWS.d/next/Library/2021-08-20-11-30-52.bpo-44449.1r2-lS.rst b/Misc/NEWS.d/next/Library/2021-08-20-11-30-52.bpo-44449.1r2-lS.rst
new file mode 100644
index 00000000000000..52f01541fca6a7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-08-20-11-30-52.bpo-44449.1r2-lS.rst
@@ -0,0 +1,2 @@
+Fix a crash in the signal handler of the :mod:`faulthandler` module: no
+longer modify the reference count of frame objects. Patch by Victor Stinner.
diff --git a/Python/traceback.c b/Python/traceback.c
index a9a9dd92e38ee9..83f3074f43d050 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -799,7 +799,10 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
PUTS(fd, "Stack (most recent call first):\n");
}
- frame = PyThreadState_GetFrame(tstate);
+ // Use a borrowed reference. Avoid Py_INCREF/Py_DECREF, since this function
+ // can be called in a signal handler by the faulthandler module which must
+ // not modify Python objects.
+ frame = tstate->frame;
if (frame == NULL) {
PUTS(fd, "<no Python frame>\n");
return;
@@ -808,17 +811,14 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header)
depth = 0;
while (1) {
if (MAX_FRAME_DEPTH <= depth) {
- Py_DECREF(frame);
PUTS(fd, " ...\n");
break;
}
if (!PyFrame_Check(frame)) {
- Py_DECREF(frame);
break;
}
dump_frame(fd, frame);
- PyFrameObject *back = PyFrame_GetBack(frame);
- Py_DECREF(frame);
+ PyFrameObject *back = frame->f_back;
if (back == NULL) {
break;
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