[PATCH v2 3/4] hw/vfio-user: wait for proxy close correctly

[John Levon <john.levon@nutanix.com>]

Coverity reported:

CID 1611806: Concurrent data access violations (BAD_CHECK_OF_WAIT_COND)

A wait is performed without a loop. If there is a spurious wakeup, the
condition may not be satisfied.

Fix this by checking ->state for VFIO_PROXY_CLOSED in a loop.

Resolves: Coverity CID 1611806
Fixes: 0b3d881a ("vfio-user: implement message receive infrastructure")
Signed-off-by: John Levon <john.levon@nutanix.com>
---
 hw/vfio-user/proxy.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/vfio-user/proxy.c b/hw/vfio-user/proxy.c
index c418954440..2275d3fe39 100644
--- a/hw/vfio-user/proxy.c
+++ b/hw/vfio-user/proxy.c
@@ -32,7 +32,6 @@ static void vfio_user_recycle(VFIOUserProxy *proxy, VFIOUserMsg *msg);
 
 static void vfio_user_recv(void *opaque);
 static void vfio_user_send(void *opaque);
-static void vfio_user_cb(void *opaque);
 
 static void vfio_user_request(void *opaque);
 
@@ -492,7 +491,7 @@ static void vfio_user_send(void *opaque)
     }
 }
 
-static void vfio_user_cb(void *opaque)
+static void vfio_user_close_cb(void *opaque)
 {
     VFIOUserProxy *proxy = opaque;
 
@@ -984,8 +983,11 @@ void vfio_user_disconnect(VFIOUserProxy *proxy)
      * handler to run after the proxy fd handlers were
      * deleted above.
      */
-    aio_bh_schedule_oneshot(proxy->ctx, vfio_user_cb, proxy);
-    qemu_cond_wait(&proxy->close_cv, &proxy->lock);
+    aio_bh_schedule_oneshot(proxy->ctx, vfio_user_close_cb, proxy);
+
+    while (proxy->state != VFIO_PROXY_CLOSED) {
+        qemu_cond_wait(&proxy->close_cv, &proxy->lock);
+    }
 
     /* we now hold the only ref to proxy */
     qemu_mutex_unlock(&proxy->lock);
-- 
2.43.0