From f16a4b26f31f95dddb12cf3c2390906a735203ae Mon Sep 17 00:00:00 2001 From: Bjorn Andersson Date: Mon, 13 Jan 2020 23:57:02 -0800 Subject: net: qrtr: Make qrtr_port_lookup() use RCU The important part of qrtr_port_lookup() wrt synchronization is that the function returns a reference counted struct qrtr_sock, or fail. As such we need only to ensure that an decrement of the object's refcount happens inbetween the finding of the object in the idr and qrtr_port_lookup()'s own increment of the object. By using RCU and putting a synchronization point after we remove the mapping from the idr, but before it can be released we achieve this - with the benefit of not having to hold the mutex in qrtr_port_lookup(). Signed-off-by: Bjorn Andersson Signed-off-by: David S. Miller --- net/qrtr/qrtr.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'net/qrtr') diff --git a/net/qrtr/qrtr.c b/net/qrtr/qrtr.c index ca802798e19e..0fe08f060b8c 100644 --- a/net/qrtr/qrtr.c +++ b/net/qrtr/qrtr.c @@ -646,11 +646,11 @@ static struct qrtr_sock *qrtr_port_lookup(int port) if (port == QRTR_PORT_CTRL) port = 0; - mutex_lock(&qrtr_port_lock); + rcu_read_lock(); ipc = idr_find(&qrtr_ports, port); if (ipc) sock_hold(&ipc->sk); - mutex_unlock(&qrtr_port_lock); + rcu_read_unlock(); return ipc; } @@ -692,6 +692,10 @@ static void qrtr_port_remove(struct qrtr_sock *ipc) mutex_lock(&qrtr_port_lock); idr_remove(&qrtr_ports, port); mutex_unlock(&qrtr_port_lock); + + /* Ensure that if qrtr_port_lookup() did enter the RCU read section we + * wait for it to up increment the refcount */ + synchronize_rcu(); } /* Assign port number to socket. -- cgit v1.2.3