[PATCH] Cygwin: fhandler_termios::tcsetpgrp: check that argument is non-negative

[Ken Brown]

Return -1 with EINVAL if pgid < 0.  This fixes the gdb problem
reported here:

  https://cygwin.com/ml/cygwin/2019-07/msg00166.html
---
 winsup/cygwin/fhandler_termios.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/winsup/cygwin/fhandler_termios.cc 
b/winsup/cygwin/fhandler_termios.cc
index 4ce53433a..5b0ba5603 100644
--- a/winsup/cygwin/fhandler_termios.cc
+++ b/winsup/cygwin/fhandler_termios.cc
@@ -69,6 +69,11 @@ fhandler_termios::tcsetpgrp (const pid_t pgid)
       set_errno (EPERM);
       return -1;
     }
+  else if (pgid < 0)
+    {
+      set_errno (EINVAL);
+      return -1;
+    }
   int res;
   while (1)
     {
-- 
2.21.0