vhost_net: validate sock before trying to put its fd

Sock will be NULL if we pass -1 to vhost_net_set_backend(), but when
we meet errors during ubuf allocation, the code does not check for
NULL before calling sockfd_put(), this will lead NULL
dereferencing. Fixing by checking sock pointer before.

Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 686dc670fd29..29756d88799b 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1226,7 +1226,8 @@ err_used:
         if (ubufs)
                 vhost_net_ubuf_put_wait_and_free(ubufs);
 err_ubufs:
-        sockfd_put(sock);
+        if (sock)
+                sockfd_put(sock);
 err_vq:
         mutex_unlock(&vq->mutex);
 err: