[PATCH 3.13 088/187] Bluetooth: Avoid use of session socket after the session gets freed

Kamal Mostafa
2014-09-15T22:17:25Z

From: Vignesh Raman <Vignesh_Raman@mentor.com>

commit 32333edb82fb2009980eefc5518100068147ab82 upstream.

The commits 08c30aca9e698faddebd34f81e1196295f9dc063 "Bluetooth: Remove
RFCOMM session refcnt" and 8ff52f7d04d9cc31f1e81dcf9a2ba6335ed34905
"Bluetooth: Return RFCOMM session ptrs to avoid freed session"
allow rfcomm_recv_ua and rfcomm_session_close to delete the session
(and free the corresponding socket) and propagate NULL session pointer
to the upper callers.

Additional fix is required to terminate the loop in rfcomm_process_rx
function to avoid use of freed 'sk' memory.

The issue is only reproducible with kernel option CONFIG_PAGE_POISONING
enabled making freed memory being changed and filled up with fixed char
value used to unmask use-after-free issues.

Signed-off-by: Vignesh Raman <Vignesh_Raman@mentor.com>
Signed-off-by: Vitaly Kuzmichev <Vitaly_Kuzmichev@mentor.com>
Acked-by: Dean Jenkins <Dean_Jenkins@mentor.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
net/bluetooth/rfcomm/core.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index facd8a7..b088651 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -1859,10 +1859,13 @@ static struct rfcomm_session *rfcomm_process_rx(struct rfcomm_session *s)
/* Get data directly from socket receive queue without copying it. */
while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
skb_orphan(skb);
- if (!skb_linearize(skb))
+ if (!skb_linearize(skb)) {
s = rfcomm_recv_frame(s, skb);
- else
+ if (!s)
+ break;
+ } else {
kfree_skb(skb);
+ }
}

if (s && (sk->sk_state == BT_CLOSED))
--
1.9.1