Bluetooth: Verify dlci not in use before rfcomm_dev create

Only one session/channel combination may be in use at any one
time. However, the failure does not occur until the tty is
opened (in rfcomm_dlc_open()).

Because these settings are actually bound at rfcomm device
creation (via RFCOMMCREATEDEV ioctl), validate and fail before
creating the rfcomm tty device.

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

3 files changed, 34 insertions, 1 deletions

diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index 0d69936831fa..f8262a2783ec 100644
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -241,6 +241,7 @@ int  rfcomm_dlc_send(struct rfcomm_dlc *d, struct sk_buff *skb);
 int  rfcomm_dlc_set_modem_status(struct rfcomm_dlc *d, u8 v24_sig);
 int  rfcomm_dlc_get_modem_status(struct rfcomm_dlc *d, u8 *v24_sig);
 void rfcomm_dlc_accept(struct rfcomm_dlc *d);
+struct rfcomm_dlc *rfcomm_dlc_exists(bdaddr_t *src, bdaddr_t *dst, u8 channel);
 
 #define rfcomm_dlc_lock(d)     spin_lock(&d->lock)
 #define rfcomm_dlc_unlock(d)   spin_unlock(&d->lock)
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index ba115d472f7b..b378bbb6f8a7 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -360,6 +360,11 @@ static struct rfcomm_dlc *rfcomm_dlc_get(struct rfcomm_session *s, u8 dlci)
         return NULL;
 }
 
+static int rfcomm_check_channel(u8 channel)
+{
+        return channel < 1 || channel > 30;
+}
+
 static int __rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst, u8 channel)
 {
         struct rfcomm_session *s;
@@ -369,7 +374,7 @@ static int __rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst,
         BT_DBG("dlc %p state %ld %pMR -> %pMR channel %d",
                d, d->state, src, dst, channel);
 
-        if (channel < 1 || channel > 30)
+        if (rfcomm_check_channel(channel))
                 return -EINVAL;
 
         if (d->state != BT_OPEN && d->state != BT_CLOSED)
@@ -514,6 +519,25 @@ no_session:
         return r;
 }
 
+struct rfcomm_dlc *rfcomm_dlc_exists(bdaddr_t *src, bdaddr_t *dst, u8 channel)
+{
+        struct rfcomm_session *s;
+        struct rfcomm_dlc *dlc = NULL;
+        u8 dlci;
+
+        if (rfcomm_check_channel(channel))
+                return ERR_PTR(-EINVAL);
+
+        rfcomm_lock();
+        s = rfcomm_session_get(src, dst);
+        if (s) {
+                dlci = __dlci(!s->initiator, channel);
+                dlc = rfcomm_dlc_get(s, dlci);
+        }
+        rfcomm_unlock();
+        return dlc;
+}
+
 int rfcomm_dlc_send(struct rfcomm_dlc *d, struct sk_buff *skb)
 {
         int len = skb->len;
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 6ea08b05b53a..a58d693e1e61 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -385,6 +385,14 @@ static int rfcomm_create_dev(struct sock *sk, void __user *arg)
                 dlc = rfcomm_pi(sk)->dlc;
                 rfcomm_dlc_hold(dlc);
         } else {
+                /* Validate the channel is unused */
+                dlc = rfcomm_dlc_exists(&req.src, &req.dst, req.channel);
+                if (IS_ERR(dlc))
+                        return PTR_ERR(dlc);
+                else if (dlc) {
+                        rfcomm_dlc_put(dlc);
+                        return -EBUSY;
+                }
                 dlc = rfcomm_dlc_alloc(GFP_KERNEL);
                 if (!dlc)
                         return -ENOMEM;