[PATCH 4.19 61/72] tun: wake up waitqueues after IFF_UP is set

Greg Kroah-Hartman
2019-07-02T08:13:16Z

From: Fei Li <lifei.shirley@bytedance.com>

[ Upstream commit 72b319dc08b4924a29f5e2560ef6d966fa54c429 ]

Currently after setting tap0 link up, the tun code wakes tx/rx waited
queues up in tun_net_open() when .ndo_open() is called, however the
IFF_UP flag has not been set yet. If there's already a wait queue, it
would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
Then the saving vhost_poll_start() will add the wq into wqh until it
is waken up again. Although this works when IFF_UP flag has been set
when tun_chr_poll detects; this is not true if IFF_UP flag has not
been set at that time. Sadly the latter case is a fatal error, as
the wq will never be waken up in future unless later manually
setting link up on purpose.

Fix this by moving the wakeup process into the NETDEV_UP event
notifying process, this makes sure IFF_UP has been set before all
waited queues been waken up.

Signed-off-by: Fei Li <lifei.shirley@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/tun.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1024,18 +1024,8 @@ static void tun_net_uninit(struct net_de
/* Net device open. */
static int tun_net_open(struct net_device *dev)
{
- struct tun_struct *tun = netdev_priv(dev);
- int i;
-
netif_tx_start_all_queues(dev);

- for (i = 0; i < tun->numqueues; i++) {
- struct tun_file *tfile;
-
- tfile = rtnl_dereference(tun->tfiles[i]);
- tfile->socket.sk->sk_write_space(tfile->socket.sk);
- }
-
return 0;
}

@@ -3443,6 +3433,7 @@ static int tun_device_event(struct notif
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct tun_struct *tun = netdev_priv(dev);
+ int i;

if (dev->rtnl_link_ops != &tun_link_ops)
return NOTIFY_DONE;
@@ -3452,6 +3443,14 @@ static int tun_device_event(struct notif
if (tun_queue_resize(tun))
return NOTIFY_BAD;
break;
+ case NETDEV_UP:
+ for (i = 0; i < tun->numqueues; i++) {
+ struct tun_file *tfile;
+
+ tfile = rtnl_dereference(tun->tfiles[i]);
+ tfile->socket.sk->sk_write_space(tfile->socket.sk);
+ }
+ break;
default:
break;
}