[Bug 1983100] Re: dotnet build intermittently crashes with segfault on Ubuntu 18.04

Thu May 11 20:38:54 UTC 2023

Thanks for the revised debdiff, Tom! I appreciate that you added a short
description of each patch to the bug, it's really helpful!

We'll need to adjust a few things before proceeding, a few comments
below.

On the debian changelog:
- Since we have many patch files, it would be good to pull the descriptive entry to the top, and list the files underneath
- We should include the LP bug number in the new changelog entry. This should be in the format "(LP: #1983100)", preferably at the end of your topmost entry

On the DEP-3 headers:
- let's point the Origin tags to the commit id of each change, so that a reviewer will be able to find the original commits in a local repo (without going through a github pull request), e.g.:
Origin: upstream, https://github.com/openssl/openssl/commit/56806f432b6c
- for the Bug-Ubuntu tag, we should use the short-link version:
Bug-Ubuntu: https://bugs.launchpad.net/bugs/1983100

On the patches themselves:

I've noticed that patch 4/7 isn't from the same PR series as the rest (it's from PR 7626 [0]), so we should correct the Origin header in that patch file. PR 7626 also has another commit that doesn't seem to be included in the debdiff, did you run tests to ensure it isn't needed for them to work properly?
[0] https://github.com/openssl/openssl/pull/7626

I'm also not fully convinced patch 7/7 is required for this SRU, as it's
specifically targeted to Windows systems. I don't think our builds
define _WIN32, so I'd imagine the patch would only introduce dead code.
Could we drop it from the next version?

Finally, I'd like to double check the patches that are focused on
shlibloadtest (patches 1, 3-7). I understand some of them aren't related
to the new NO_ATEXIT change, but are fixing the underlying test that's
used by that specific patch. Does this mean that shlibloadtest is
currently broken for bionic? Or are these patches needed for the
additional tests introduced by patch 5?

Ultimately, I wonder if it would be appropriate to e.g. spin the
shlibloadtest fixes into a separate LP bug, or if the NO_ATEXIT tests
will just outright break without them. Could you please confirm whether
this is the case?

Thanks again for all the work on this, Tom! Given we're touching a
critical component (openssl) of an LTS release that's soon to move out
of standard support, we'll have to be a bit more strict than usual and
this SRU is likely to receive extra attention, so thanks for being
understanding about it.

Cheers,
Heitor

** Changed in: openssl (Ubuntu Bionic)
       Status: In Progress => Incomplete

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https://bugs.launchpad.net/bugs/1983100

Title:
  dotnet build intermittently crashes with segfault on Ubuntu 18.04

Status in openssl package in Ubuntu:
  Fix Released
Status in openssl source package in Bionic:
  Incomplete

Bug description:
  [Impact]

  Bionic's OpenSSL 1.1.1 package
  (https://launchpad.net/ubuntu/bionic/+source/openssl) is the only
  version of openssl 1.1.1 on any distro that we've encountered that
  does not have support for the OPENSSL_NO_ATEXIT functionality from
  1.1.1b (openssl/openssl at c2b3db2).

  The threading model in .NET has the possibility that background
  threads are still running when exit() is called, which can cause
  SIGSEGV if a background thread interacts with OpenSSL after/while it
  has unloaded. For that reason, we always initialize OpenSSL 1.1.1 with
  the OPENSSL_NO_ATEXIT flag (which, of all the distros we run on only
  has no effect on Bionic).

  We feel that the stability of applications on Ubuntu 18.04 would be
  improved if the functionality of OPENSSL_NO_ATEXIT was merged into the
  bionic openssl 1.1.1 package, even if the constant isn't published
  into the header for the dev package.

  Context:
  https://github.com/dotnet/runtime/issues/48411#issuecomment-1178405101

  [Test Plan]

  The described behavior can be reproduced by passing the
  OPENSSL_NO_ATEXIT to the OPENSSL_init_ssl() call. The application will
  terminate with a SEGFAULT. More concretely, a minimal reproducer is:

  #include <stdio.h>
  #include <openssl/err.h>
  #include <openssl/ssl.h>

  #ifndef OPENSSL_INIT_NO_ATEXIT
  #define OPENSSL_INIT_NO_ATEXIT 0x00080000L
  #endif

  static void print_error_string()
  {
      printf("print_error_string:\n");
      printf("ERR_reason_error_string(0) => %s\n", ERR_reason_error_string(0));
  }

  int main(int argc, char* argv[])
  {
      // register this handler first, so it runs last.
      atexit(print_error_string);

      OPENSSL_init_ssl(
              OPENSSL_INIT_ADD_ALL_CIPHERS |
              OPENSSL_INIT_ADD_ALL_DIGESTS |
              OPENSSL_INIT_LOAD_CONFIG |
              OPENSSL_INIT_NO_ATEXIT |
              OPENSSL_INIT_LOAD_CRYPTO_STRINGS |
              OPENSSL_INIT_LOAD_SSL_STRINGS,
          NULL);

      print_error_string();

      return 0;
  }

  Building

  $ sudo apt install libssl-dev
  $ gcc test.c -lssl -lcrypto
  $ ./a.out
  print_error_string:
  ERR_reason_error_string(0) => (null)
  print_error_string:
  Segmentation fault (core dumped)

  [Other Info]
  All of these patches are included in upstream release 1.1.1b
  - lp1983100-0001-Fix-shlibloadtest-to-properly-execute-the-dso_ref-te.patch
    Fixes the shlibloadtest that was updated as part of #0005

  - lp1983100-0002-Implement-OPENSSL_INIT_NO_ATEXIT.patch
    Patch adds the OPENSSL_INIT_NO_ATEXIT option

  - lp1983100-0003-Don-t-link-shlibloadtest-against-libcrypto.patch
    Additional fixes for shlibloadtest

  - lp1983100-0004-Fix-rpath-related-Linux-test_shlibload-failure.patch
    Additional fixes for shlibloadtest

  - lp1983100-0005-Test-atexit-handlers.patch
    Adds test for OPENSSL_INIT_NO_ATEXIT option and updates the shlibloadtest

  - lp1983100-0006-Introduce-a-no-pinshared-option.patch
    This patch includes tests to ensure that if OPENSSL_INIT_NO_ATEXIT is not defined then the atexit() handler is run

  - lp1983100-0007-Support-_onexit-in-preference-to-atexit-on-Windows.patch
    This patch ensures that atexit() is only called when on non-Windows systems as Windows uses _onexit() during library unloading

  All seven patches are required to ensure the correct logic and
  operation of the OPENSSL_INIT_NO_ATEXIT option.

  [Where problems could occur]

  The patches adds an option to the OPENSSL_init_crypto() function to
  disable the default behavior of calling of a cleanup function on
  application exit. The patch also includes a few bug fixes around
  various initializations that were supposed to happen once when running
  threaded but were not.

  These changes have the potential for regressions and it is conceivable
  that they lead to incorrect behavior. However, I have also backported
  and included all new testing functions in the hope that the changed
  behavior will get appropriate testing.

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