[PATCH] 9pfs/proxy: Check return value of proxy_marshal()

[Greg Kurz]

This should always successfully write exactly two 32-bit integers.
Make it clear with an assert(), like v9fs_receive_status() and
v9fs_receive_response() already do when unmarshalling the same
header.

Fixes: Coverity CID 1438968
Signed-off-by: Greg Kurz <gr...@kaod.org>
---
 hw/9pfs/9p-proxy.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
index 6f598a0f111c..4aa4e0a3baa0 100644
--- a/hw/9pfs/9p-proxy.c
+++ b/hw/9pfs/9p-proxy.c
@@ -537,7 +537,8 @@ static int v9fs_request(V9fsProxy *proxy, int type, void 
*response, ...)
     }
 
     /* marshal the header details */
-    proxy_marshal(iovec, 0, "dd", header.type, header.size);
+    retval = proxy_marshal(iovec, 0, "dd", header.type, header.size);
+    assert(retval == 4 * 2);
     header.size += PROXY_HDR_SZ;
 
     retval = qemu_write_full(proxy->sockfd, iovec->iov_base, header.size);