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>

1 files changed, 9 insertions, 2 deletions

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index b385d9985656..d9d4bc89e638 100644
--- 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);