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authorPeter Hurley <peter@hurleysoftware.com>2014-02-09 20:59:05 -0500
committerMarcel Holtmann <marcel@holtmann.org>2014-02-14 13:39:29 -0800
commit082a1532fc7607727f759c069eb8dd9fa5ae3f37 (patch)
tree15f3c98d06aac088502669dd8e35291e399bd734 /net/bluetooth/rfcomm/tty.c
parentc0fdfb80382e4901473ce0e31d1e7833c1d297be (diff)
Bluetooth: Fix racy acquire of rfcomm_dev reference
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> Tested-By: Alexander Holler <holler@ahsoftware.de> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Diffstat (limited to 'net/bluetooth/rfcomm/tty.c')
-rw-r--r--net/bluetooth/rfcomm/tty.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index a535ef148ef6..7cf193f0eea7 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);