[PATCH] nbd/server: improve nbd_negotiate_send_rep_list

[Vladimir Sementsov-Ogievskiy]

Don't try to write zero-lenght strings.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
 nbd/server.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/nbd/server.c b/nbd/server.c
index 24ebc1a805..28a915f5a2 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -392,14 +392,18 @@ static int nbd_negotiate_send_rep_list(NBDClient *client, 
NBDExport *exp,
         return -EINVAL;
     }
 
-    if (nbd_write(ioc, name, name_len, errp) < 0) {
-        error_prepend(errp, "write failed (name buffer): ");
-        return -EINVAL;
+    if (name_len > 0) {
+        if (nbd_write(ioc, name, name_len, errp) < 0) {
+            error_prepend(errp, "write failed (name buffer): ");
+            return -EINVAL;
+        }
     }
 
-    if (nbd_write(ioc, desc, desc_len, errp) < 0) {
-        error_prepend(errp, "write failed (description buffer): ");
-        return -EINVAL;
+    if (desc_len > 0) {
+        if (nbd_write(ioc, desc, desc_len, errp) < 0) {
+            error_prepend(errp, "write failed (description buffer): ");
+            return -EINVAL;
+        }
     }
 
     return 0;
-- 
2.21.0