A race condition exists between near simultaneous asynchronous
DLC data channel disconnection requests from the host and remote device.
This causes the socket layer to request a socket shutdown at the same
time the rfcomm core is processing the disconnect request from the remote
device.
The socket layer retains a copy of a struct rfcomm_dlc d pointer.
The d pointer refers to a copy of a struct rfcomm_session.
When the socket layer thread performs a socket shutdown, the thread
may wait on a rfcomm lock in rfcomm_dlc_close(). This means that
whilst the thread waits, the rfcomm_session and/or rfcomm_dlc structures
pointed to by d maybe freed due to rfcomm core handling. Consequently,
when the rfcomm lock becomes available and the thread runs, a
malfunction could occur as a freed rfcomm_session structure and/or a
freed rfcomm_dlc structure will be erroneously accessed.
Therefore, after the rfcomm lock is acquired, check that the struct
rfcomm_session is still valid by searching the rfcomm session list.
If the session is valid then validate the d pointer by searching the
rfcomm session list of active DLCs for the rfcomm_dlc structure
pointed by d.
Signed-off-by: Dean Jenkins <Dean_Jenkins@xxxxxxxxxx>
Acked-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
---
net/bluetooth/rfcomm/core.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index 8780e67..ae7124e 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -493,12 +493,34 @@ static int __rfcomm_dlc_close(struct rfcomm_dlc *d, int err)
int rfcomm_dlc_close(struct rfcomm_dlc *d, int err)
{
- int r;
+ int r = 0;
+ struct rfcomm_dlc *d_list;
+ struct rfcomm_session *s, *s_list;
+
+ BT_DBG("dlc %p state %ld dlci %d err %d", d, d->state, d->dlci, err);
rfcomm_lock();
- r = __rfcomm_dlc_close(d, err);
+ s = d->session;
+ if (!s)
+ goto no_session;
+
+ /* after waiting on the mutex check the session still exists
+ * then check the dlc still exists
+ */
+ list_for_each_entry(s_list, &session_list, list) {
+ if (s_list == s) {
+ list_for_each_entry(d_list, &s->dlcs, list) {
+ if (d_list == d) {
+ r = __rfcomm_dlc_close(d, err);
+ break;
+ }
+ }
+ break;
+ }
+ }
+no_session:
rfcomm_unlock();
return r;
}
--
1.7.10.1
--
To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
