Messages in this thread Patch in this message | | | From | Peter Hurley <> | Subject | [PATCH 05/24] Bluetooth: Fix racy acquire of rfcomm_dev reference | Date | Sun, 9 Feb 2014 20:59:05 -0500 |
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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 <jslaby@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> --- 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
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