From 8051a2a518fcf3827a143470083ad6008697ff17 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Thu, 12 Mar 2015 11:53:41 +1030 Subject: [PATCH] 9p/trans_virtio: fix hot-unplug On device hot-unplug, 9p/virtio currently will kfree channel while it might still be in use. Of course, it might stay used forever, so it's an extremely ugly hack, but it seems better than use-after-free that we have now. [ Unused variable removed, whitespace cleanup, msg single-lined --RR ] Signed-off-by: Michael S. Tsirkin Signed-off-by: Rusty Russell --- net/9p/trans_virtio.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index d8e376a5f0f1..36a1a739ad68 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -658,14 +658,30 @@ p9_virtio_create(struct p9_client *client, const char *devname, char *args) static void p9_virtio_remove(struct virtio_device *vdev) { struct virtio_chan *chan = vdev->priv; - - if (chan->inuse) - p9_virtio_close(chan->client); - vdev->config->del_vqs(vdev); + unsigned long warning_time; mutex_lock(&virtio_9p_lock); + + /* Remove self from list so we don't get new users. */ list_del(&chan->chan_list); + warning_time = jiffies; + + /* Wait for existing users to close. */ + while (chan->inuse) { + mutex_unlock(&virtio_9p_lock); + msleep(250); + if (time_after(jiffies, warning_time + 10 * HZ)) { + dev_emerg(&vdev->dev, + "p9_virtio_remove: waiting for device in use.\n"); + warning_time = jiffies; + } + mutex_lock(&virtio_9p_lock); + } + mutex_unlock(&virtio_9p_lock); + + vdev->config->del_vqs(vdev); + sysfs_remove_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr); kobject_uevent(&(vdev->dev.kobj), KOBJ_CHANGE); kfree(chan->tag);