[Bug 1842730]

[Cvs-commit]

The master branch has been updated by Florian Weimer
<fw at sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f63b73814f74032c0e5d0a83300e3d864ef905e5

commit f63b73814f74032c0e5d0a83300e3d864ef905e5
Author: Florian Weimer <fweimer at redhat.com>
Date:   Wed Nov 13 15:44:56 2019 +0100

    Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]
    
    This introduces a “pending NODELETE” state in the link map, which is
    flipped to the persistent NODELETE state late in dlopen, via
    activate_nodelete.    During initial relocation, symbol binding
    records pending NODELETE state only.  dlclose ignores pending NODELETE
    state.  Taken together, this results that a partially completed dlopen
    is rolled back completely because new NODELETE mappings are unloaded.
    
    Tested on x86_64-linux-gnu and i386-linux-gnu.
    
    Change-Id: Ib2a3d86af6f92d75baca65431d74783ee0dbc292

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https://bugs.launchpad.net/bugs/1842730

Title:
  glibc: dlopen crash after a previously failed call to dlopen

Status in GLibC:
  Fix Released
Status in glibc package in Ubuntu:
  New

Bug description:
  Environment
  ===========

  Ubuntu 18.04.3 LTS
  Linux 4.15.0-60-generic #67-Ubuntu SMP Thu Aug 22 16:55:30 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
  libc6:amd64 2.27-3ubuntu1
  gcc 4:7.4.0-1ubuntu2.3

  Steps to reproduce the crash
  ============================

  (note: all libraries are linked with --no-as-needed to keep them as
  DT_NEEDED entries in the dynamic section, even though they are
  unused.)

  1) create an empty library libNOTFOUND.so
  2) create an empty library libB.so, linked to libNOTFOUND.so
  3) create an empty library libA.so, linked to glibc's librt.so
  4) create an empty library libPLUGIN.so, linked to libA.so and libB.so, set DT_RUNPATH to '$ORIGIN'
  5) create an empty library libMAIN.so
  6) create an executable, linked to libMAIN.so and libdl.so, set DT_RUNPATH to '$ORIGIN', this program calls:
     a) dlopen("<absolute path to>/libPLUGIN.so")
     b) dlopen("<absolute path to>/libMAIN.so")

  Behaviour
  =========

  a) dlopen("<absolute path to>/libPLUGIN.so") fails because it cannot find libNOTFOUND.so via default search methods. This is wanted and OK!
  b) dlopen("<absolute path to>/libMAIN.so") raises SIGSEGV somewhere deep inside the dynamic linking code of glibc (backtrace attached). Expected result: returns a valid handle to libMAIN.so.

  Comments
  ========

  Attached is a simple test script which does all the steps from above
  and also shows the workaround: Ensure that librt.so is loaded and
  fully initialized before the failing call to
  dlopen("<...>/libPLUGIN.so") happens. This can be done either via
  LD_PRELOAD or by linking the executable to librt.so.

  You can also replace librt.so with libpthread.so to reproduce this
  behaviour. Any other library I tried instead of librt.so (e.g.
  libm.so) does not trigger this bug.

  I also attached a trace with LD_DEBUG=all. Here you can see that glibc
  tries to relocate librt.so while it loads libMAIN.so. I would expect
  that librt.so is loaded/relocated when libPLUGIN.so is dlopen'ed or
  that it is neither loaded nor relocated because libPLUGIN.so has unmet
  dependencies.

  This example is a stripped down version of a real scenario where an
  application was misconfigured.

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