l2cap_sock_kill can be called in l2cap_sock_release and l2cap_sock_close_cb
either. This lead l2cap_chan_destroy to be called twice for same channel.
To prevent double list_del and double chan_put, chan_destroy should be protected
with chan->refcnt and chan_list_lock so that reentrance could be forbidden.
Signed-off-by: Minho Ban <[email protected]>
---
net/bluetooth/l2cap_core.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 24f144b..156ca14 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -400,10 +400,14 @@ struct l2cap_chan *l2cap_chan_create(void)
void l2cap_chan_destroy(struct l2cap_chan *chan)
{
write_lock(&chan_list_lock);
+ /* Check if channel is valid */
+ if (!atomic_read(&chan->refcnt)) {
+ write_unlock(&chan_list_lock);
+ return;
+ }
list_del(&chan->global_l);
- write_unlock(&chan_list_lock);
-
l2cap_chan_put(chan);
+ write_unlock(&chan_list_lock);
}
void l2cap_chan_set_defaults(struct l2cap_chan *chan)
--
1.7.5.4
On 05/22/2012 09:23 PM, Chanyeol Park wrote:
> Hi
>
> On 2012년 05월 22일 11:50, Minho Ban wrote:
>> @@ -1343,10 +1343,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
>> l2cap_chan_lock(chan);
>>
>> l2cap_chan_del(chan, err);
>> + chan->ops->close(chan->data);
>>
>> l2cap_chan_unlock(chan);
>>
>> - chan->ops->close(chan->data);
>> l2cap_chan_put(chan);
>> }
> I think this patch does not make sense Because inside chan->ops->close() "chan" could be freed in the l2cap_chan_destroy().
>
I agree, thanks for pointing out.
Hi
On 2012년 05월 22일 11:50, Minho Ban wrote:
> @@ -1343,10 +1343,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
> l2cap_chan_lock(chan);
>
> l2cap_chan_del(chan, err);
> + chan->ops->close(chan->data);
>
> l2cap_chan_unlock(chan);
>
> - chan->ops->close(chan->data);
> l2cap_chan_put(chan);
> }
I think this patch does not make sense Because inside chan->ops->close()
"chan" could be freed in the l2cap_chan_destroy().
> close callback must locate within chan_lock unless it can be scheduled to other thread
> which may wait for chan_lock in l2cap_sock_shutdown and this lead to duplicate sock_kill.
>
> static void l2cap_sock_kill(struct sock *sk)
> {
> - if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
> + if (!sock_flag(sk, SOCK_ZAPPED) || sock_flag(sk, SOCK_DEAD) ||
> + sk->sk_socket)
> return;
>
> BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
>
> Duplicate sock_kill may happen anyway, need test SOCK_DEAD if chan_destroy is already called.
Even l2cap_sock_kill() is called twice, " if (!sock_flag(sk,
SOCK_ZAPPED) || sk->sk_socket)" can't filter it.
I tested Mr.ban case. it works fine with me.
BR
Chanyeol Park.
On 05/22/2012 01:21 AM, Gustavo Padovan wrote:
> Hi Minho,
>
> * Minho Ban <[email protected]> [2012-05-21 09:56:40 +0900]:
>
>> l2cap_sock_kill can be called in l2cap_sock_release and l2cap_sock_close_cb
>> either. This lead l2cap_chan_destroy to be called twice for same channel.
>> To prevent double list_del and double chan_put, chan_destroy should be protected
>> with chan->refcnt and chan_list_lock so that reentrance could be forbidden.
>
> Even if l2cap_sock_kill() is called twice it will call l2cap_chan_destroy()
> only once. If this is not happening we just have a broken piece of code
> somewhere else and not here.
>
> Gustavo
>
Thanks for comment but I could not found any suitable code in l2cap_sock_kill that
can make l2cap_chan_destroy to be called just once. sock flag test is not enough to
do it.
I agree this path should not be the fix. Testing chan->refcnt is nonsense because
chan might have been freed already. So I looked for another point,
@@ -1343,10 +1343,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
l2cap_chan_lock(chan);
l2cap_chan_del(chan, err);
+ chan->ops->close(chan->data);
l2cap_chan_unlock(chan);
- chan->ops->close(chan->data);
l2cap_chan_put(chan);
}
close callback must locate within chan_lock unless it can be scheduled to other thread
which may wait for chan_lock in l2cap_sock_shutdown and this lead to duplicate sock_kill.
static void l2cap_sock_kill(struct sock *sk)
{
- if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
+ if (!sock_flag(sk, SOCK_ZAPPED) || sock_flag(sk, SOCK_DEAD) ||
+ sk->sk_socket)
return;
BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
Duplicate sock_kill may happen anyway, need test SOCK_DEAD if chan_destroy is already called.
Regards,
Minho Ban
Hi Minho,
* Minho Ban <[email protected]> [2012-05-21 09:56:40 +0900]:
> l2cap_sock_kill can be called in l2cap_sock_release and l2cap_sock_close_cb
> either. This lead l2cap_chan_destroy to be called twice for same channel.
> To prevent double list_del and double chan_put, chan_destroy should be protected
> with chan->refcnt and chan_list_lock so that reentrance could be forbidden.
Even if l2cap_sock_kill() is called twice it will call l2cap_chan_destroy()
only once. If this is not happening we just have a broken piece of code
somewhere else and not here.
Gustavo