[Bug 1854326] Re: [UBUNTU] - glibc: z15 (s390x) strstr implementation can return incorrect result if search string cross page boundary

[Ernst Sjöstrand]

That i386 build failure in eoan-proposed is quite annoying:

https://launchpad.net/ubuntu/+source/glibc/2.30-0ubuntu2.1/+build/18674640

Makes build-essential uninstallable for example...

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Title:
  [UBUNTU] - glibc: z15 (s390x) strstr implementation can return
  incorrect result if search string cross page boundary

Status in Ubuntu on IBM z Systems:
  Fix Committed
Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Eoan:
  Fix Committed

Bug description:
  [Impact]

  glibc: strstr(): Invalid result if needle crosses page on s390-z15 ifunc variant.
  If the specified needle crosses a page-boundary, the s390-z15 ifunc variant of
  strstr truncates the needle which results in invalid results.

  Example:
  needle = "Hello" <page-boundary> "World"
  really used needle = "Hello"
  haystack = "abc HelloBug def"
  result = "HelloBug def"

  This only happens if the needle before page-boundary contains 9 or
  less characters.

  See upstream-glibc bugzilla "Bug 25226 - strstr: Invalid result if needle crosses page on s390-z15 ifunc variant."
  (https://sourceware.org/bugzilla/show_bug.cgi?id=25226)

  Fixed with upstream-glibc commit "S390: Fix handling of needles crossing a page in strstr z15 ifunc-variant. [BZ #25226]"
  (https://sourceware.org/git/?p=glibc.git;a=commit;h=bfdb731438206b0f70fe7afa890681155c30b419)

  Please backport this commit to Ubuntu 19.10, which includes glibc 2.30

  Already backported to upstream-glibc-release-branch-2.30:
  https://sourceware.org/git/?p=glibc.git;a=commit;h=f4419b0d0181da28f18cba40068f2e75300f5020

  glibc 2.31 (tentativ GA 2020-02-01) will have this fix integrated.
  If this version will not be picked finally, then this fix is also needed for 20.04

  [Test Case]

   * glibc builds and passes testsuite, as the commit to backport
  includes comprehensive testsuite for the problem in question in the
  glibc api.

  [Regression Potential]

   * Fix released in focal, and available from stable upstream branches.
   * all autopkgtests will be triggered, implying that comprehensive test coverage will execute on all architectues.

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