[PATCH 1/1] Cygwin: Fix cygheap corruption caused by cloned atomic buffer

[David McFarland <corngood at gmail dot com>]

The fhandler_base_overlapped::copyto clears atomic_write_buf on the
clone, but none of the derived classes were doing this.  This allowed
the destructor to double-free the buffer and corrupt cygheap.
Clear atomic_write_buf in copyto of all derived classes.
---
 winsup/cygwin/fhandler.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 2cc99d713..9e63867ab 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1216,6 +1216,7 @@ public:
   {
     x->pc.free_strings ();
     *reinterpret_cast<fhandler_pipe *> (x) = *this;
+    reinterpret_cast<fhandler_pipe *> (x)->atomic_write_buf = NULL;
     x->reset (this);
   }
 
@@ -1256,6 +1257,7 @@ public:
   {
     x->pc.free_strings ();
     *reinterpret_cast<fhandler_fifo *> (x) = *this;
+    reinterpret_cast<fhandler_fifo *> (x)->atomic_write_buf = NULL;
     x->reset (this);
   }
 
-- 
2.19.1