Public bug reported: 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. ** Affects: glibc (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1756209 Title: i386 implementation of memmove broken since glibc 2.21 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1756209/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
