2014-01-12 13:20:08

by Dean Jenkins

Subject: [PATCH] Bluetooth: Avoid use of session socket after the session gets freed

From: Vitaly Kuzmichev <[email protected]>

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: Vitaly Kuzmichev <[email protected]>
Acked-by: Dean Jenkins <[email protected]>
---
net/bluetooth/rfcomm/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index facd8a7..5632146 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -1857,7 +1857,7 @@ static struct rfcomm_session *rfcomm_process_rx(struct rfcomm_session *s)
BT_DBG("session %p state %ld qlen %d", s, s->state, skb_queue_len(&sk->sk_receive_queue));

/* Get data directly from socket receive queue without copying it. */
- while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
+ while (s && (skb = skb_dequeue(&sk->sk_receive_queue))) {
skb_orphan(skb);
if (!skb_linearize(skb))
s = rfcomm_recv_frame(s, skb);
--
1.8.1.5

2014-01-16 06:23:00

by Marcel Holtmann

Subject: Re: [PATCH] Bluetooth: Avoid use of session socket after the session gets freed

Hi Dean,

> 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: Vitaly Kuzmichev <[email protected]>
> Acked-by: Dean Jenkins <[email protected]>
> ---
> net/bluetooth/rfcomm/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
> index facd8a7..5632146 100644
> --- a/net/bluetooth/rfcomm/core.c
> +++ b/net/bluetooth/rfcomm/core.c
> @@ -1857,7 +1857,7 @@ static struct rfcomm_session *rfcomm_process_rx(struct rfcomm_session *s)
> BT_DBG("session %p state %ld qlen %d", s, s->state, skb_queue_len(&sk->sk_receive_queue));
>
> /* Get data directly from socket receive queue without copying it. */
> - while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
> + while (s && (skb = skb_dequeue(&sk->sk_receive_queue))) {
> skb_orphan(skb);
> if (!skb_linearize(skb))
> s = rfcomm_recv_frame(s, skb);

Let do a break here.

if (!s)
break;

Regards

Marcel