Comment 0 for bug 1756209

In glibc 2.21 they optimized i386 memcpy:

https://sourceware.org/ml/libc-alpha/2015-02/msg00119.html

The implementation contained a bug which causes memmove to break when crossing the 2GB threshold.

This has been filed with glibc here (filed by someone else, but I have requested an update from them as well):

https://sourceware.org/bugzilla/show_bug.cgi?id=22644

Unfortunately they have not yet taken action on this bug, however I want to bring it to your attention in the hope that it can be patched into all current Ubuntu releases as soon as possible. I hope this is not improper procedure. Both myself and another (see comment 1 in the glibc bug report) have tested the patch provided in the above glibc bug report and it does appear to fix the problem, however I don't know what the procedure is for getting it properly confirmed/tested and merged into Ubuntu.

As requested in the guidelines:

1) We are using:
Description: Ubuntu 16.04.4 LTS
Release: 16.04

2)
libc6:i386:
  Installed: 2.23-0ubuntu10

However as stated above this has been present since libc6:i386 2.21 and affects Ubuntu 15.04 onward. (I have actually tested this as well. 15.04 conveniently used both glibc 2.19 and 2.21 so it was a good test platform when I was initially attempting to track down the problem.)

3) What we expected to happen:
memmove should move data within the entire valid address space without segfaulting or corrupting memory.

4) What happened instead:
When memmove attempts to move data crossing the 2GB threshold it either segfaults or causes memory corruption.