merge branch 'pr-2481'

Tianjia Zhang (1):
  nsenter: fix repeat close() operations

LGTMs: @kolyshkin @cyphar
Closes #2481

libcontainer/nsenter/nsexec.c

@@ -714,12 +714,12 @@ void nsexec(void)
 			 * ready, so we can receive all possible error codes
 			 * generated by children.
 			 */
+			syncfd = sync_child_pipe[1];
+			close(sync_child_pipe[0]);
+
 			while (!ready) {
 				enum sync_t s;
 
-				syncfd = sync_child_pipe[1];
-				close(sync_child_pipe[0]);
-
 				if (read(syncfd, &s, sizeof(s)) != sizeof(s))
 					bail("failed to sync with child: next state");
 
@@ -789,13 +789,13 @@ void nsexec(void)
 
 			/* Now sync with grandchild. */
 
+			syncfd = sync_grandchild_pipe[1];
+			close(sync_grandchild_pipe[0]);
+
 			ready = false;
 			while (!ready) {
 				enum sync_t s;
 
-				syncfd = sync_grandchild_pipe[1];
-				close(sync_grandchild_pipe[0]);
-
 				s = SYNC_GRANDCHILD;
 				if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
 					kill(child, SIGKILL);