Return-Path: From: Peter Hurley To: Marcel Holtmann Cc: Gustavo Padovan , Johan Hedberg , Gianluca Anzolin , Alexander Holler , Andrey Vihrov , Sander Eikelenboom , linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Hurley , Jiri Slaby , Greg Kroah-Hartman Subject: [PATCH 05/24] Bluetooth: Fix racy acquire of rfcomm_dev reference Date: Sun, 9 Feb 2014 20:59:05 -0500 Message-Id: <1391997564-1805-6-git-send-email-peter@hurleysoftware.com> In-Reply-To: <1391997564-1805-1-git-send-email-peter@hurleysoftware.com> References: <1391997564-1805-1-git-send-email-peter@hurleysoftware.com> List-ID: rfcomm_dev_get() can return a rfcomm_dev reference for a device for which destruction may be commencing. This can happen on tty destruction, which calls rfcomm_tty_cleanup(), the last port reference may have been released but RFCOMM_TTY_RELEASED was not set. The following race is also possible: CPU 0 | CPU 1 | rfcomm_release_dev rfcomm_dev_get | . spin_lock | . dev = __rfcomm_dev_get | . if dev | . if test_bit(TTY_RELEASED) | . | !test_and_set_bit(TTY_RELEASED) | tty_port_put <<<< last reference else | tty_port_get | The reference acquire is bogus because destruction will commence with the release of the last reference. Ignore the external state change of TTY_RELEASED and instead rely on the reference acquire itself to determine if the reference is valid. Cc: Jiri Slaby Cc: Greg Kroah-Hartman Signed-off-by: Peter Hurley --- net/bluetooth/rfcomm/tty.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c index a535ef1..7cf193f 100644 --- a/net/bluetooth/rfcomm/tty.c +++ b/net/bluetooth/rfcomm/tty.c @@ -157,12 +157,8 @@ static struct rfcomm_dev *rfcomm_dev_get(int id) dev = __rfcomm_dev_get(id); - if (dev) { - if (test_bit(RFCOMM_TTY_RELEASED, &dev->flags)) - dev = NULL; - else - tty_port_get(&dev->port); - } + if (dev && !tty_port_get(&dev->port)) + dev = NULL; spin_unlock(&rfcomm_dev_lock); -- 1.8.1.2