[PATCH 4.9 094/108] tipc: fix connection refcount error

Greg Kroah-Hartman
2017-06-15T18:04:39Z

From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>

[ Upstream commit fc0adfc8fd18b61b6f7a3f28b429e134d6f3a008 ]

Until now, the generic server framework maintains the connection
id's per subscriber in server's conn_idr. At tipc_close_conn, we
remove the connection id from the server list, but the connection is
valid until we call the refcount cleanup. Hence we have a window
where the server allocates the same connection to an new subscriber
leading to inconsistent reference count. We have another refcount
warning we grab the refcount in tipc_conn_lookup() for connections
with flag with CF_CONNECTED not set. This usually occurs at shutdown
when the we stop the topology server and withdraw TIPC_CFG_SRV
publication thereby triggering a withdraw message to subscribers.

In this commit, we:
1. remove the connection from the server list at recount cleanup.
2. grab the refcount for a connection only if CF_CONNECTED is set.

Tested-by: John Thompson <thompa.atl@gmail.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/server.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

--- a/net/tipc/server.c
+++ b/net/tipc/server.c
@@ -91,7 +91,8 @@ static void tipc_sock_release(struct tip
static void tipc_conn_kref_release(struct kref *kref)
{
struct tipc_conn *con = container_of(kref, struct tipc_conn, kref);
- struct sockaddr_tipc *saddr = con->server->saddr;
+ struct tipc_server *s = con->server;
+ struct sockaddr_tipc *saddr = s->saddr;
struct socket *sock = con->sock;
struct sock *sk;

@@ -106,6 +107,11 @@ static void tipc_conn_kref_release(struc
tipc_sock_release(con);
sock_release(sock);
con->sock = NULL;
+
+ spin_lock_bh(&s->idr_lock);
+ idr_remove(&s->conn_idr, con->conid);
+ s->idr_in_use--;
+ spin_unlock_bh(&s->idr_lock);
}

tipc_clean_outqueues(con);
@@ -128,8 +134,10 @@ static struct tipc_conn *tipc_conn_looku

spin_lock_bh(&s->idr_lock);
con = idr_find(&s->conn_idr, conid);
- if (con)
+ if (con && test_bit(CF_CONNECTED, &con->flags))
conn_get(con);
+ else
+ con = NULL;
spin_unlock_bh(&s->idr_lock);
return con;
}
@@ -198,15 +206,8 @@ static void tipc_sock_release(struct tip

static void tipc_close_conn(struct tipc_conn *con)
{
- struct tipc_server *s = con->server;
-
if (test_and_clear_bit(CF_CONNECTED, &con->flags)) {

- spin_lock_bh(&s->idr_lock);
- idr_remove(&s->conn_idr, con->conid);
- s->idr_in_use--;
- spin_unlock_bh(&s->idr_lock);
-
/* We shouldn't flush pending works as we may be in the
* thread. In fact the races with pending rx/tx work structs
* are harmless for us here as we have already deleted this