Open Stack

Hi, I'd like you to take a look at this patch for potential
SecurityImpact.
https://review.openstack.org/153502

Log:
commit 4a414a0fa556e664358c53745f73408224057314
Author: Alexander Tivelkov <ativelkov at mirantis.com>
Date:   Tue Jan 20 18:25:07 2015 +0300

    Fix for CooperativeReader to process read length
    
    CooperativeReader, being an eventlet-friendly wrapper around the
    generator- based reader of image data, actually transforms
    chunk-by-chunk iteration into the readable stream. It is used when the
    image is being copied from the remote source: some generator-based
    image data representing the remote source acts as its underlying
    object, and the instance of CooperativeReader is passed as a data
    stream to the backend client which uses it to read the data.
    
    Before this patch, the CooperativeReader was ignoring the "length"
    parameter of the read method, always returning the whole chunk returned
    by the underlying generator (in case of HTTP source the size of this
    chunk is 16 M). This was causing problems for the clients attempting to
    read data from it, and - under some circumstances - the loss of data.
    
    For chunked storage of files in Swift a special class (ChunkReader,
    declared in the swift store driver) is used to reduce the requested
    read length so no extra data is read and transferred. However, this was
    not working as the CooperativeReader (which was the underlying stream
    for the ChunkReader) was ignoring the requested size. This was causing
    the data to be lost when reading behind the boundaries of the Chunks.
    
    This patchset introduces a buffer in the CooperativeReader to store the
    most recently fetched iterator chunk. The reads are independent from
    requests to iterator, so the CooperativeReader is able to return the
    exact requested amount of bytes and no data is lost due to extra-reads.
    
    SecurityImpact
    
    Change-Id: Ief37d1e29487bb03e612320f5cc06910cfd1c23a
    Closes-bug: #1412802
    (cherry picked from commit 270ec44)