From c06f7d532aa6f78b2847e3b651c0da27fc3296c0 Mon Sep 17 00:00:00 2001 From: Dean Jenkins Date: Thu, 28 Feb 2013 14:21:54 +0000 Subject: [PATCH] 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 Acked-by: Marcel Holtmann Signed-off-by: Gustavo Padovan --- 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 d301fbbe2098..d9e97cf1792b 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; } -- 2.30.2