From: Cristy <urban-warrior@imagemagick.org>
Date: Sat, 3 Feb 2018 18:51:02 +0000 (-0500)
Subject: ...
X-Git-Tag: 7.0.7-23~160
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=66595914939217f5f08639801c98c1a3f351c411;p=imagemagick

...
---

diff --git a/MagickCore/blob.c b/MagickCore/blob.c
index 2bb35466a..cb0465917 100644
--- a/MagickCore/blob.c
+++ b/MagickCore/blob.c
@@ -118,6 +118,9 @@ struct _BlobInfo
     extent,
     quantum;
 
+  BlobMode
+    mode;
+
   MagickBooleanType
     mapped,
     eof;
@@ -653,6 +656,7 @@ MagickExport MagickBooleanType CloseBlob(Image *image)
   blob_info->size=GetBlobSize(image);
   image->extent=blob_info->size;
   blob_info->eof=MagickFalse;
+  blob_info->mode=UndefinedBlobMode;
   if (blob_info->exempt != MagickFalse)
     {
       blob_info->type=UndefinedStream;
@@ -3063,6 +3067,7 @@ MagickExport MagickBooleanType OpenBlob(const ImageInfo *image_info,
       return(MagickTrue);
     }
   (void) DetachBlob(blob_info);
+  blob_info->mode=mode;
   switch (mode)
   {
     default: type="r"; break;
@@ -4698,14 +4703,30 @@ MagickExport MagickOffsetType SeekBlob(Image *image,
           break;
         }
       }
-      if (blob_info->offset < (MagickOffsetType) ((off_t) blob_info->length))
+      if (blob_info->offset <= (MagickOffsetType) ((off_t) blob_info->length))
         {
           blob_info->eof=MagickFalse;
           break;
         }
-      if (blob_info->offset < (MagickOffsetType) ((off_t) blob_info->extent))
-        break;
-      return(-1);
+      if ((image->blob->mapped == MagickFalse) &&
+          ((image->blob->mode == WriteBlobMode) ||
+           (image->blob->mode == WriteBinaryBlobMode)))
+        {
+          image->blob->extent=(size_t) (image->blob->offset+
+            image->blob->quantum);
+          image->blob->quantum<<=1;
+          image->blob->data=(unsigned char *) ResizeQuantumMemory(
+            image->blob->data,image->blob->extent+1,sizeof(*image->blob->data));
+          (void) SyncBlob(image);
+          if (image->blob->data == (unsigned char *) NULL)
+            {
+              (void) DetachBlob(image->blob);
+              return(-1);
+            }
+        }
+      if (blob_info->offset > (MagickOffsetType) ((off_t) blob_info->extent))
+        return(-1);
+      break;
     }
     case CustomStream:
     {