Commit 0771d7df authored by Tuong Lien's avatar Tuong Lien Committed by David S. Miller

tipc: fix memory leak in service subscripting

Upon receipt of a service subscription request from user via a topology
connection, one 'sub' object will be allocated in kernel, so it will be
able to send an event of the service if any to the user correspondingly
then. Also, in case of any failure, the connection will be shutdown and
all the pertaining 'sub' objects will be freed.

However, there is a race condition as follows resulting in memory leak:

       receive-work       connection        send-work
              |                |                |
        sub-1 |<------//-------|                |
        sub-2 |<------//-------|                |
              |                |<---------------| evt for sub-x
        sub-3 |<------//-------|                |
              :                :                :
              :                :                :
              |       /--------|                |
              |       |        * peer closed    |
              |       |        |                |
              |       |        |<-------X-------| evt for sub-y
              |       |        |<===============|
        sub-n |<------/        X    shutdown    |
    -> orphan |                                 |

That is, the 'receive-work' may get the last subscription request while
the 'send-work' is shutting down the connection due to peer close.

We had a 'lock' on the connection, so the two actions cannot be carried
out simultaneously. If the last subscription is allocated e.g. 'sub-n',
before the 'send-work' closes the connection, there will be no issue at
all, the 'sub' objects will be freed. In contrast the last subscription
will become orphan since the connection was closed, and we released all
references.

This commit fixes the issue by simply adding one test if the connection
remains in 'connected' state right after we obtain the connection lock,
then a subscription object can be created as usual, otherwise we ignore
it.
Acked-by: default avatarYing Xue <ying.xue@windriver.com>
Acked-by: default avatarJon Maloy <jmaloy@redhat.com>
Reported-by: default avatarThang Ngo <thang.h.ngo@dektech.com.au>
Signed-off-by: default avatarTuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c7268589
......@@ -400,6 +400,8 @@ static int tipc_conn_rcv_from_sock(struct tipc_conn *con)
return -EWOULDBLOCK;
if (ret == sizeof(s)) {
read_lock_bh(&sk->sk_callback_lock);
/* RACE: the connection can be closed in the meantime */
if (likely(connected(con)))
ret = tipc_conn_rcv_sub(srv, con, &s);
read_unlock_bh(&sk->sk_callback_lock);
if (!ret)
......
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