Bluetooth: Take proper tty_struct references

In net/bluetooth/rfcomm/tty.c the struct tty_struct is used without
taking references. This may lead to a use-after-free of the rfcomm tty.

Fix this by taking references properly, using the tty_port_* helpers
when possible.

The raw assignments of dev->port.tty in rfcomm_tty_open/close are
addressed in the later commit 'rfcomm: Implement .activate, .shutdown
and .carrier_raised methods'.

Signed-off-by: Gianluca Anzolin <gianluca@sottospazio.it>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

1 files changed, 17 insertions, 12 deletions

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index b6e44ad6cca6..cd7ff370be38 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -333,10 +333,9 @@ static inline unsigned int rfcomm_room(struct rfcomm_dlc *dlc)
 static void rfcomm_wfree(struct sk_buff *skb)
 {
         struct rfcomm_dev *dev = (void *) skb->sk;
-        struct tty_struct *tty = dev->port.tty;
         atomic_sub(skb->truesize, &dev->wmem_alloc);
-        if (test_bit(RFCOMM_TTY_ATTACHED, &dev->flags) && tty)
-                tty_wakeup(tty);
+        if (test_bit(RFCOMM_TTY_ATTACHED, &dev->flags))
+                tty_port_tty_wakeup(&dev->port);
         tty_port_put(&dev->port);
 }
 
@@ -410,6 +409,7 @@ static int rfcomm_release_dev(void __user *arg)
 {
         struct rfcomm_dev_req req;
         struct rfcomm_dev *dev;
+        struct tty_struct *tty;
 
         if (copy_from_user(&req, arg, sizeof(req)))
                 return -EFAULT;
@@ -429,8 +429,11 @@ static int rfcomm_release_dev(void __user *arg)
                 rfcomm_dlc_close(dev->dlc, 0);
 
         /* Shut down TTY synchronously before freeing rfcomm_dev */
-        if (dev->port.tty)
-                tty_vhangup(dev->port.tty);
+        tty = tty_port_tty_get(&dev->port);
+        if (tty) {
+                tty_vhangup(tty);
+                tty_kref_put(tty);
+        }
 
         if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
                 rfcomm_dev_del(dev);
@@ -563,6 +566,7 @@ static void rfcomm_dev_data_ready(struct rfcomm_dlc *dlc, struct sk_buff *skb)
 static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
 {
         struct rfcomm_dev *dev = dlc->owner;
+        struct tty_struct *tty;
         if (!dev)
                 return;
 
@@ -572,7 +576,8 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
         wake_up_interruptible(&dev->wait);
 
         if (dlc->state == BT_CLOSED) {
-                if (!dev->port.tty) {
+                tty = tty_port_tty_get(&dev->port);
+                if (!tty) {
                         if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags)) {
                                 /* Drop DLC lock here to avoid deadlock
                                  * 1. rfcomm_dev_get will take rfcomm_dev_lock
@@ -591,8 +596,10 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
                                 tty_port_put(&dev->port);
                                 rfcomm_dlc_lock(dlc);
                         }
-                } else
-                        tty_hangup(dev->port.tty);
+                } else {
+                        tty_hangup(tty);
+                        tty_kref_put(tty);
+                }
         }
 }
 
@@ -604,10 +611,8 @@ static void rfcomm_dev_modem_status(struct rfcomm_dlc *dlc, u8 v24_sig)
 
         BT_DBG("dlc %p dev %p v24_sig 0x%02x", dlc, dev, v24_sig);
 
-        if ((dev->modem_status & TIOCM_CD) && !(v24_sig & RFCOMM_V24_DV)) {
-                if (dev->port.tty && !C_CLOCAL(dev->port.tty))
-                        tty_hangup(dev->port.tty);
-        }
+        if ((dev->modem_status & TIOCM_CD) && !(v24_sig & RFCOMM_V24_DV))
+                tty_port_tty_hangup(&dev->port, true);
 
         dev->modem_status =
                 ((v24_sig & RFCOMM_V24_RTC) ? (TIOCM_DSR | TIOCM_DTR) : 0) |