From e41f43a1a675ee6d0f21f2ab611c97ffe9c22088 Mon Sep 17 00:00:00 2001
From: Christopher Faylor <me@cgf.cx>
Date: Fri, 21 Aug 2009 21:19:45 +0000
Subject: [PATCH] * fcntl.cc (fcntl64): Detect negative fd as error.

---
 winsup/cygwin/ChangeLog | 4 ++++
 winsup/cygwin/fcntl.cc  | 8 +++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 9c08c56da..316a48a3e 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,7 @@
+2009-08-21  Christopher Faylor  <me+cygwin@cgf.cx>
+
+	* fcntl.cc (fcntl64): Detect negative fd as error.
+
 2009-08-21  Corinna Vinschen  <corinna@vinschen.de>
 
 	* mmap.cc (mmap64): Allocate fh_disk_file on cygheap.  Delete
diff --git a/winsup/cygwin/fcntl.cc b/winsup/cygwin/fcntl.cc
index 442686268..bb41f05c5 100644
--- a/winsup/cygwin/fcntl.cc
+++ b/winsup/cygwin/fcntl.cc
@@ -40,7 +40,13 @@ fcntl64 (int fd, int cmd, ...)
   switch (cmd)
     {
     case F_DUPFD:
-      res = dup2 (fd, cygheap_fdnew (((int) arg) - 1));
+      if ((int) arg >= 0)
+	res = dup2 (fd, cygheap_fdnew (((int) arg) - 1));
+      else
+	{
+	  set_errno (EINVAL);
+	  res = -1;
+	}
       break;
     case F_GETLK:
     case F_SETLK: