From: Eryu Guan <eguan@linux.alibaba.com>

Date: Mon, 27 Jan 2020 19:02:25 +0000

Subject: [PATCH] virtiofsd: stop all queue threads on exit in virtio_loop()

On guest graceful shutdown, virtiofsd receives VHOST_USER_GET_VRING_BASE

request from VMM and shuts down virtqueues by calling fv_set_started(),

which joins fv_queue_thread() threads. So when virtio_loop() returns,

there should be no thread is still accessing data in fuse session and/or

virtio dev.

But on abnormal exit, e.g. guest got killed for whatever reason,

vhost-user socket is closed and virtio_loop() breaks out the main loop

and returns to main(). But it's possible fv_queue_worker()s are still

working and accessing fuse session and virtio dev, which results in

crash or use-after-free.

Fix it by stopping fv_queue_thread()s before virtio_loop() returns,

to make sure there's no-one could access fuse session and virtio dev.

Reported-by: Qingming Su <qingming.su@linux.alibaba.com>

Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit 9883df8ccae6d744a0c8d9cbf9d62b1797d70ebd)

---

 tools/virtiofsd/fuse_virtio.c | 13 +++++++++++++

 1 file changed, 13 insertions(+)

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c

index 9f6582343c..80a6e929df 100644

--- a/tools/virtiofsd/fuse_virtio.c

+++ b/tools/virtiofsd/fuse_virtio.c

@@ -815,6 +815,19 @@ int virtio_loop(struct fuse_session *se)

         }

     }

+    /*

+     * Make sure all fv_queue_thread()s quit on exit, as we're about to

+     * free virtio dev and fuse session, no one should access them anymore.

+     */

+    for (int i = 0; i < se->virtio_dev->nqueues; i++) {

+        if (!se->virtio_dev->qi[i]) {

+            continue;

+        }

+

+        fuse_log(FUSE_LOG_INFO, "%s: Stopping queue %d thread\n", __func__, i);

+        fv_queue_cleanup_thread(se->virtio_dev, i);

+    }

+

     fuse_log(FUSE_LOG_INFO, "%s: Exit\n", __func__);

     return 0;