[PULL 17/17] net/vdpa: fix potential fd leak in net_init_vhost_vdpa()

["Michael S. Tsirkin" <mst@redhat.com>]

From: Stefano Garzarella <sgarzare@redhat.com>

Coverity reported a file descriptor leak (CID 1490785) that happens if
`vhost_vdpa_get_max_queue_pairs()` returns 0, since in that case
net_host_vdpa_init(), which should take ownership of the fd, is never
called.

vhost_vdpa_get_max_queue_pairs() returns 1 if VIRTIO_NET_F_MQ is not
negotiated, or a negative error if the ioctl() fails, or the maximum
number of queue pairs exposed by the device in the config space in the
`max_virtqueue_pairs` field. In the VIRTIO spec we have:
     The device MUST set max_virtqueue_pairs to between 1 and 0x8000
     inclusive, if it offers VIRTIO_NET_F_MQ.

So, if `vhost_vdpa_get_max_queue_pairs()` returns 0, it's really an
error since the device is violating the VIRTIO spec.

Treat also `queue_pairs == 0` as an error, and jump to the `err` label,
to return a negative value to the caller in any case.

Coverity: CID 1490785
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20250714101156.30024-1-sgarzare@redhat.com>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 net/vhost-vdpa.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 6a30a44d2b..74d26a9497 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -1840,9 +1840,8 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
 
     queue_pairs = vhost_vdpa_get_max_queue_pairs(vdpa_device_fd, features,
                                                  &has_cvq, errp);
-    if (queue_pairs < 0) {
-        qemu_close(vdpa_device_fd);
-        return queue_pairs;
+    if (queue_pairs <= 0) {
+        goto err;
     }
 
     r = vhost_vdpa_get_iova_range(vdpa_device_fd, &iova_range);
-- 
MST