From 62fcf3d9638b87cd7ac81962cadf5bf88db62fa0 Mon Sep 17 00:00:00 2001
From: Cristy <urban-warrior@imagemagick.org>
Date: Fri, 21 Jul 2017 19:56:25 -0400
Subject: [PATCH] https://github.com/ImageMagick/ImageMagick/issues/596

---
 coders/png.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/coders/png.c b/coders/png.c
index b9158086a..3d33163ce 100644
--- a/coders/png.c
+++ b/coders/png.c
@@ -3253,7 +3253,12 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
 
   status=SetImageExtent(image,image->columns,image->rows,exception);
   if (status == MagickFalse)
-    return(DestroyImageList(image));
+    {
+#ifdef IMPNG_SETJMP_NOT_THREAD_SAFE
+      UnlockSemaphoreInfo(ping_semaphore);
+#endif
+      return(DestroyImageList(image));
+    }
 
   if (num_passes > 1)
     pixel_info=AcquireVirtualMemory(image->rows,ping_rowbytes*
-- 
2.40.0