[Bug 2001975] Re: overflow bug in wcsncmp_avx2

[Brian Murray]

Hello Simon, or anyone else affected,

Accepted glibc into focal-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/glibc/2.31-0ubuntu9.10
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: glibc (Ubuntu Focal)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-focal

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https://bugs.launchpad.net/bugs/2001975

Title:
  overflow bug in wcsncmp_avx2

Status in GLibC:
  Fix Released
Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Focal:
  Fix Committed

Bug description:
  [Impact]

  See https://sourceware.org/bugzilla/show_bug.cgi?id=28755

  Note that we're only impacted by the avx2 issue, the evex-optimized
  version isn't present in the 2.31 branch.

  [Test case]

  > test_wcsncmp.c cat <<EOF
  #include <wchar.h>
  #include <assert.h>

  int
  main(int argc, char ** argv) {
      assert(__wcsncmp_avx2(L"abc", L"abd", (1UL << 62)) != 0);
  }
  EOF
  gcc -static -o test_wcsncmp test_wcsncmp.c
  ./test_scsncmp

  [Regression potential]

  The patch is contained within the AVX-2 optimized routine, but it
  could still cause introduce a new bug there. In addition, we could see
  performance regressions.

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