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 pointer and/or a
freed d pointer will be erroneously reused.
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.
If active DLCs exist when the rfcomm session is terminating,
avoid a memory leak of rfcomm_dlc structures by ensuring that
rfcomm_session_close() is used instead of rfcomm_session_del().
Signed-off-by: Dean Jenkins <djenkins@xxxxxxxxxx>
---
net/bluetooth/rfcomm/core.c | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)
diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index c7921fd..1a7db34 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -496,11 +496,34 @@ 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;
+ struct list_head *p, *n, *p2, *n2;
rfcomm_lock();
- r = __rfcomm_dlc_close(d, err);
+ s = d->session;
+ if (s) {
+ /* check the session still exists after waiting on the mutex */
+ list_for_each_safe(p, n, &session_list) {
+ s_list = list_entry(p, struct rfcomm_session, list);
+ if (s == s_list) {
+ /* check the dlc still exists */
+ /* after waiting on the mutex */
+ list_for_each_safe(p2, n2, &s->dlcs) {
+ d_list = list_entry(p2,
+ struct rfcomm_dlc,
+ list);
+ if (d == d_list) {
+ r = __rfcomm_dlc_close(d, err);
+ break;
+ }
+ }
+ break;
+ }
+ }
+ }
rfcomm_unlock();
return r;
@@ -1155,7 +1178,7 @@ static struct rfcomm_session *rfcomm_recv_ua(struct rfcomm_session *s, u8 dlci)
break;
case BT_DISCONN:
- s = rfcomm_session_del(s);
+ s = rfcomm_session_close(s, ECONNRESET);
break;
}
}
--
1.7.10.1
--
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