From: Tuong Lien tuong.t.lien@dektech.com.au
[ Upstream commit 0771d7df819284d46cf5cfb57698621b503ec17f ]
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: Ying Xue ying.xue@windriver.com Acked-by: Jon Maloy jmaloy@redhat.com Reported-by: Thang Ngo thang.h.ngo@dektech.com.au Signed-off-by: Tuong Lien tuong.t.lien@dektech.com.au Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- net/tipc/topsrv.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c index 41f4464ac6cc..ec9a7137d267 100644 --- a/net/tipc/topsrv.c +++ b/net/tipc/topsrv.c @@ -407,7 +407,9 @@ static int tipc_conn_rcv_from_sock(struct tipc_conn *con) return -EWOULDBLOCK; if (ret == sizeof(s)) { read_lock_bh(&sk->sk_callback_lock); - ret = tipc_conn_rcv_sub(srv, con, &s); + /* 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) return 0;