From 8e8bf8cfd8c07b65cdde21066cf4a25b63b3fec5 Mon Sep 17 00:00:00 2001 From: Pierre-Marie de Rodat Date: Tue, 21 Jun 2016 12:32:56 +0200 Subject: [PATCH] Fix use of a dangling pointer for Python breakpoint objects When a Python script tries to create a breakpoint but fails to do so, gdb.Breakpoint.__init__ raises an exception and the breakpoint does not exist anymore in the Python interpreter. However, GDB still keeps a reference to the Python object to be used for a later hook, which is wrong. This commit adds the necessary cleanup code so that there is no stale reference to this Python object. It also adds a new testcase to reproduce the bug and check the fix. 2016-06-24 Pierre-Marie de Rodat gdb/ * python/py-breakpoint.c (bppy_init): Clear bppy_pending_object when there is an error during the breakpoint creation. gdb/testsuite * gdb.python/py-breakpoint-create-fail.c, gdb.python/py-breakpoint-create-fail.exp, gdb.python/py-breakpoint-create-fail.py: New testcase. --- gdb/python/py-breakpoint.c | 1 + .../gdb.python/py-breakpoint-create-fail.c | 28 +++++++++++ .../gdb.python/py-breakpoint-create-fail.exp | 58 ++++++++++++++++++++++ .../gdb.python/py-breakpoint-create-fail.py | 31 ++++++++++++ 4 files changed, 118 insertions(+) create mode 100644 gdb/testsuite/gdb.python/py-breakpoint-create-fail.c create mode 100644 gdb/testsuite/gdb.python/py-breakpoint-create-fail.exp create mode 100644 gdb/testsuite/gdb.python/py-breakpoint-create-fail.py diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c index ed9cae6..5918bcc 100644 --- a/gdb/python/py-breakpoint.c +++ b/gdb/python/py-breakpoint.c @@ -705,6 +705,7 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs) } CATCH (except, RETURN_MASK_ALL) { + bppy_pending_object = NULL; PyErr_Format (except.reason == RETURN_QUIT ? PyExc_KeyboardInterrupt : PyExc_RuntimeError, "%s", except.message); diff --git a/gdb/testsuite/gdb.python/py-breakpoint-create-fail.c b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.c new file mode 100644 index 0000000..c346bdd --- /dev/null +++ b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.c @@ -0,0 +1,28 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2016 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +int +foo (int a) +{ + return a * 2; +} + +int +main (void) +{ + return foo (2); +} diff --git a/gdb/testsuite/gdb.python/py-breakpoint-create-fail.exp b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.exp new file mode 100644 index 0000000..68cdccd --- /dev/null +++ b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.exp @@ -0,0 +1,58 @@ +# Copyright (C) 2016 Free Software Foundation, Inc. +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +# This file is part of the GDB testsuite. It tests proper handling for +# breakpoint creation failure. + +load_lib gdb-python.exp + +standard_testfile + +if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } { + return -1 +} + +# Skip all tests if Python scripting is not enabled. +if { [skip_python_tests] } { continue } + +clean_restart "${testfile}" +if ![runto_main] { + perror "could not run to main" + continue +} + +# The following will create a breakpoint Python wrapper whose construction will +# abort: the requested symbol is not defined. GDB should not keep a reference +# to the wrapper; however it used to... +gdb_test "source py-breakpoint2.py" + +# ... and when it did, as a result, the following breakpoint creation (not +# initiated by the Python API) would dereference the already-freed Python +# breakpoint wrapper, resulting in undefined behavior, sometimes observed as a +# gdb crash, and other times causing the next stop to invoke the Python wrapper +# "stop" method for the object that is not supposed to exist. +gdb_test "break foo" + +# ... eventually, triggering this breakpoint will invoke the Python wrapper +# "stop" method for an object that is not supposed to exist. +set test "continuing to foo" +gdb_test_multiple "continue" "$test" { + -re "MyBP\.stop was invoked\!.*$gdb_prompt $" { + fail "$test" + } + -re "Continuing.*Breakpoint 2, foo.*$gdb_prompt $" { + pass "$test" + } +} diff --git a/gdb/testsuite/gdb.python/py-breakpoint-create-fail.py b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.py new file mode 100644 index 0000000..845eb0f --- /dev/null +++ b/gdb/testsuite/gdb.python/py-breakpoint-create-fail.py @@ -0,0 +1,31 @@ +# Copyright (C) 2016 Free Software Foundation, Inc. +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +import gdb + + +class MyBP(gdb.Breakpoint): + def stop(self): + print('MyBP.stop was invoked!') + # Don't make this breakpoint stop + return False + + +try: + bp = MyBP('does_not_exist', gdb.BP_WATCHPOINT) +except RuntimeError: + pass +else: + assert False -- 2.8.3