[Bug 2001975] Re: overflow bug in wcsncmp_avx2

[Launchpad Bug Tracker]

This bug was fixed in the package glibc - 2.31-0ubuntu9.12

---------------
glibc (2.31-0ubuntu9.12) focal; urgency=medium

  * Drop SVE memcpy implementation due to kernel-related performance
    regression

glibc (2.31-0ubuntu9.11) focal; urgency=medium

  * Drop memcmp arm64 SIMD optimization patch due to performance regression
    on Raspberry Pi 3+ and 4

glibc (2.31-0ubuntu9.10) focal; urgency=medium

  [ Andrei Gherzan ]
  * d/p/lp1910312: Backport upstream fix for SEM_STAT_ANY (LP: #1910312)

  [ Simon Chopin ]
  * d/p/lp1999551/*: backport mem{cmp,cpy} optimizations for arm64 (LP: #1999551)
  * d/p/lp2001932/*: fix segfault in AVX2 strncmp (LP: #2001932)
  * d/p/lp2001975/*: fix overflow in AVX2 wcsncmp (LP: #2001975)

 -- Simon Chopin <schopin at ubuntu.com>  Wed, 26 Jul 2023 09:44:39 +0200

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

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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 Released

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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