From c67dbd41f13f5302120ad40fee94ea6c7ffc2bfc Mon Sep 17 00:00:00 2001 From: Jason Fried Date: Wed, 5 Feb 2020 03:38:25 -0800 Subject: [PATCH] Add some gc safety around _mysql__fetch_row (#348) Users of gc.get_referrers() could cause a SystemError to be raised if this function is running in a different python thread. --- MySQLdb/_mysql.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/MySQLdb/_mysql.c b/MySQLdb/_mysql.c index 13280ace..1556fda3 100644 --- a/MySQLdb/_mysql.c +++ b/MySQLdb/_mysql.c @@ -1373,9 +1373,15 @@ _mysql_ResultObject_fetch_row( convert_row = row_converters[how]; if (maxrows) { if (!(r = PyTuple_New(maxrows))) goto error; - rowsadded = _mysql__fetch_row(self, &r, skiprows, maxrows, - convert_row); + + // see: https://docs.python.org/3/library/gc.html#gc.get_referrers + // This function can get a reference to the tuple r, and if that + // code is preempted while holding a ref to r, the _PyTuple_Resize + // will raise a SystemError because the ref count is 2. + PyObject_GC_UnTrack(r); + rowsadded = _mysql__fetch_row(self, &r, skiprows, maxrows, convert_row); if (rowsadded == -1) goto error; + PyObject_GC_Track(r); } else { if (self->use) { maxrows = 1000;