[Bug 702617] New: Wrong buffer size and loop index in _get_merged_memory in gstbuffer.c

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=702617
  GStreamer | gstreamer (core) | 1.0.7

           Summary: Wrong buffer size and loop index in _get_merged_memory
                    in gstbuffer.c
    Classification: Platform
           Product: GStreamer
           Version: 1.0.7
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: visechelle at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=247230)
 View: https://bugzilla.gnome.org/attachment.cgi?id=247230
 Review: https://bugzilla.gnome.org/review?bug=702617&attachment=247230

Patch

As explain in the title, it seems the size field and the condition to leave the
for loop in _get_merged_memory of gstbuffer.c are wrong.
I noticed this with a custom element which was parsing the RTP buffers after
rtph264pay element. rtph264pay or another element before might store the
payload in more than one blocksize and when retrieving the payload in my
element with gst_rtp_buffer_get_payload(), it merges internally the memory
blocks containing the payload if necessary.
When the payload was stored in more than one block size, it was leading to get
a buffer bigger of RTP header length size than before and messing up my data
inside.
In the patch provided in attachment, I applied the following changes:

 - Set the size of the buffer containing the merged memory of the size of the
memory blocks to be merged (and not the size of the full buffer)

 - Change the condition to leave the for loop from (i < length) to (i <
idx+length) to handle cases where i > 0.

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