Bluetooth: Release rfcomm_dev only once

No logic prevents an rfcomm_dev from being released multiple
times. For example, if the rfcomm_dev ref count is large due
to pending tx, then multiple RFCOMMRELEASEDEV ioctls may
mistakenly release the rfcomm_dev too many times. Note that
concurrent ioctls are not required to create this condition.

Introduce RFCOMM_DEV_RELEASED status bit which guarantees the
rfcomm_dev can only be released once.

NB: Since the flags are exported to userspace, introduce the status
field to track state for which userspace should not be aware.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Tested-By: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index c312cfc..b9759eb 100644 (file)
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -324,11 +324,15 @@ int  rfcomm_connect_ind(struct rfcomm_session *s, u8 channel,
 #define RFCOMMGETDEVINFO       _IOR('R', 211, int)
 #define RFCOMMSTEALDLC         _IOW('R', 220, int)
 
+/* rfcomm_dev.flags bit definitions */
 #define RFCOMM_REUSE_DLC      0
 #define RFCOMM_RELEASE_ONHUP  1
 #define RFCOMM_HANGUP_NOW     2
 #define RFCOMM_TTY_ATTACHED   3
-#define RFCOMM_TTY_RELEASED   4
+#define RFCOMM_DEFUNCT_BIT4   4          /* don't reuse this bit - userspace visible */
+
+/* rfcomm_dev.status bit definitions */
+#define RFCOMM_DEV_RELEASED   0
 
 struct rfcomm_dev_req {
        s16      dev_id;

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index b385d99..d9d4bc8 100644 (file)
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -51,6 +51,8 @@ struct rfcomm_dev {
        unsigned long           flags;
        int                     err;
 
+       unsigned long           status;         /* don't export to userspace */
+
        bdaddr_t                src;
        bdaddr_t                dst;
        u8                      channel;
@@ -423,6 +425,12 @@ static int rfcomm_release_dev(void __user *arg)
                return -EPERM;
        }
 
+       /* only release once */
+       if (test_and_set_bit(RFCOMM_DEV_RELEASED, &dev->status)) {
+               tty_port_put(&dev->port);
+               return -EALREADY;
+       }
+
        if (req.flags & (1 << RFCOMM_HANGUP_NOW))
                rfcomm_dlc_close(dev->dlc, 0);
 
@@ -433,8 +441,7 @@ static int rfcomm_release_dev(void __user *arg)
                tty_kref_put(tty);
        }
 
-       if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) &&
-           !test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
+       if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
                tty_port_put(&dev->port);
 
        tty_port_put(&dev->port);