>>> Hi,
>>>
>>> In my case it looks OK, this is the diff:
>>>
>>> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
>>> index f1b1edd0b697..32ef3328ab49 100644
>>> --- a/net/bluetooth/l2cap_sock.c
>>> +++ b/net/bluetooth/l2cap_sock.c
>>> @@ -1500,6 +1500,9 @@ static void l2cap_sock_close_cb(struct
>>> l2cap_chan *chan)
>>> {
>>> struct sock *sk = chan->data;
>>>
>>> + if (!sk)
>>> + return;
>>> +
>>> l2cap_sock_kill(sk);
>>> }
>>>
>>> @@ -1508,6 +1511,9 @@ static void l2cap_sock_teardown_cb(struct
>>> l2cap_chan *chan, int err)
>>> struct sock *sk = chan->data;
>>> struct sock *parent;
>>>
>>> + if (!sk)
>>> + return;
>>> +
>>> BT_DBG("chan %p state %s", chan, state_to_string(chan->state));
>>>
>>> /* This callback can be called both for server (BT_LISTEN)
>>> @@ -1700,6 +1706,7 @@ static void l2cap_sock_destruct(struct sock *sk)
>>> BT_DBG("sk %p", sk);
>>>
>>> if (l2cap_pi(sk)->chan)
>>> + l2cap_pi(sk)->chan->data = NULL;
>>> l2cap_chan_put(l2cap_pi(sk)->chan);
>>>
>>> But if it has potential risk if l2cap_sock_destruct() can not be
>>> excuted in time ?
>>>
>>> sk_free():
>>>
>>> if (refcount_dec_and_test(&sk->sk_wmem_alloc)) //is possible
>>> this condition false ?
>>>
>>> __sk_free(sk) -> ... l2cap_sock_destruct()
>>>
>> Dear Luiz,
>>
>> Not only that, if l2cap_sock_kill() has put 'l2cap_pi(sk)->chan', how
>> does we avoid re-puting 'l2cap_pi(sk)->chan' if l2cap_sock_destruct()
>> work postponed? this will cause underflow of chan->refcount; this PATCH
>> 4e1a720d0312 ("Bluetooth: avoid killing an already killed socket") also
>> may not work in any case because only sock_orphan() has excuted can this
>> sock be killed, but if sco_sock_release() excute first, for this sock
>> has been marked as SOCK_DEAD, this sock can never be killed. So should
>> we think put chan->data = NULL in xx_sock_kill() is a better choice ?
> Not sure what do you mean by postponed? Interrupted perhaps? Even in
> that case what are trying to prevent is use after free so if the
> callback has not run yet that means the sk has not been freed. Anyway
> I think we could do it inconditionally in l2cap_sock_kill since we
> will be releasing the reference owned by l2cap_pi(sk)->chan->data that
> should be reset to NULL immediatelly.
Dear Luiz,
yes, that's right, if sk can be accessed, it also means that chan has
not been destroyed, thanks very much.
-- Wang ShaoBo