Commit c06f7d53 authored Feb 28, 2013 by Dean Jenkins Committed by Gustavo Padovan Mar 08, 2013

Bluetooth: Check rfcomm session and DLC exists on socket close



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@mentor.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

parent fea7b02f

net/bluetooth/rfcomm/core.c

+24 −2

Original line number	Diff line number	Diff line
		@@ -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();

		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;
		}