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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>
This commit is contained in:
Dean Jenkins 2013-02-28 14:21:54 +00:00 committed by Gustavo Padovan
parent fea7b02fbf
commit c06f7d532a
1 changed files with 24 additions and 2 deletions
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26
net/bluetooth/rfcomm/core.c
View File

@ -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;
}