From c39725b398c14d9fcd466d359659b5337bd27df0 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Thu, 12 Mar 2015 07:51:23 -0600
Subject: [PATCH] libc: stdio: Fix NULL pointer dereference in ungetc(). If
 'stream' was NULL, 'stream->fs_oflags' was evaluated.  From Juha Niskanen

---
 libc/stdio/lib_ungetc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/libc/stdio/lib_ungetc.c b/libc/stdio/lib_ungetc.c
index 9d14499d7b7..bf8699a384d 100644
--- a/libc/stdio/lib_ungetc.c
+++ b/libc/stdio/lib_ungetc.c
@@ -94,10 +94,17 @@ int ungetc(int c, FAR FILE *stream)
   int nungotten;
 #endif
 
+  /* Verify that a non-NULL stream was provided */
+
+  if (!stream)
+    {
+      set_errno(EBADF);
+      return EOF;
+    }
+
   /* Stream must be open for read access */
 
-  if ((stream && stream->fs_fd < 0) ||
-      ((stream->fs_oflags & O_RDOK) == 0))
+  if ((stream->fs_fd < 0) || ((stream->fs_oflags & O_RDOK) == 0))
     {
       set_errno(EBADF);
       return EOF;