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Re: server crash in authz object pool

From: Stefan Sperling <stsp_at_apache.org>
Date: Mon, 12 Feb 2018 13:07:54 +0100

On Mon, Feb 12, 2018 at 12:50:12PM +0100, Stefan Sperling wrote:
> The svn-bb-openbsd bot has found a crash in the object pool code.
>
> It is triggered when running RA serf tests on OpenBSD. The httpd
> work processes crash due to what looks like a use-after-free (0xdf
> means this byte of memory has been freed).
>
> I can reproduce this on sparc64 and amd64 machines.
> The build is without APR_HAS_THREADS, using the prefork MPM with HTTPD 2.2.
> Let me know if you need more details. I have no time at present to hunt
> this down myself, so I'm sending this info to the list in hope that it
> will be useful.

Hmm, a quick check revealed that this started happening with r1823787,
where I stopped pre-loading libpthread.so into httpd. To the best of
my knowledge dlopen() now works without this hack on OpenBSD.

However, the httpd modules in my build *are* linked to libpthread.so
for some reason, even though APR is compiled without threads:

$ ldd modules/svn-trunk/{mod_authz_svn,mod_dav_svn,mod_dontdothat}.so | grep pthread
        00001afb97159000 00001afb97362000 rlib 0 10 0 /usr/lib/libpthread.so.25.1
        00001afb2c499000 00001afb2c6a2000 rlib 0 10 0 /usr/lib/libpthread.so.25.1
        00001afb81409000 00001afb81612000 rlib 0 3 0 /usr/lib/libpthread.so.25.1

So this could just be a local problem in my build.
I'll investigate this later, and revert r1823787 for now.

------------------------------------------------------------------------
r1823787 | stsp | 2018-02-10 18:17:17 +0100 (Sat, 10 Feb 2018) | 3 lines

* tools/dev/unix-build/Makefile.svn: Remove the LIB_PTHREAD_HACK.
  This is no longer needed.

Index: tools/dev/unix-build/Makefile.svn
===================================================================
--- tools/dev/unix-build/Makefile.svn (revision 1823786)
+++ tools/dev/unix-build/Makefile.svn (revision 1823787)
@@ -1940,17 +1940,9 @@ endif
 libpath:
         @echo export LD_LIBRARY_PATH="$(LD_LIBRARY_PATH):$$LD_LIBRARY_PATH" \
                 "PYTHONPATH=$(SVN_PREFIX)/lib/svn-python"
-#
-# OpenBSD requires an LD_PRELOAD hack to dlopen() libraries linked to
-# libpthread (e.g. libsvn_auth_gnome_keyring.so) into executables that
-# aren't linked to libpthread.
-ifeq ($(UNAME),OpenBSD)
-LIB_PTHREAD_HACK=LD_PRELOAD=libpthread.so
-endif
-
 .PHONY: start-svnserve stop-svnserve start-httpd stop-httpd
 
-HTTPD_CMD = env LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) $(LIB_PTHREAD_HACK) \
+HTTPD_CMD = env LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) \
                 $(PREFIX)/httpd/bin/apachectl
 HTTPD_START_CMD = $(HTTPD_CMD) -f $(HTTPD_CHECK_CONF) -k start
 HTTPD_START_CMD_PROXY = $(HTTPD_CMD) -f $(HTTPD_PROXY_CONF)
@@ -2007,7 +1999,7 @@ define do_check
 -cd $(svn_builddir) && for fs in fsfs bdb; do \
     echo "Begin test: $(subst svn-check-,,$@) x $$fs"; \
     test -d "$(RAMDISK)/tmp" && export TMPDIR="$(RAMDISK)/tmp"; \
- env LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) $(LIB_PTHREAD_HACK) \
+ env LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) \
         env MAKEFLAGS= make check PARALLEL=$(PARALLEL) CLEANUP=$(CLEANUP) \
           EXCLUSIVE_WC_LOCKS=$(EXCLUSIVE_WC_LOCKS) \
           SVN_BIN_DIR=$(SVN_PREFIX)/bin \
@@ -2066,7 +2058,6 @@ svn-check-swig-pl:
         -if [ $(ENABLE_PERL_BINDINGS) = yes ]; then \
                 (cd $(svn_builddir) && \
                         env LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) \
- $(LIB_PTHREAD_HACK) \
                         env MAKEFLAGS= make check-swig-pl 2>&1) | \
                                 tee $(svn_builddir)/tests.log.bindings.pl; \
         fi
@@ -2084,8 +2075,7 @@ svn-check-swig-rb:
                 env RUBYLIB=$(RUBYLIB) \
                 LD_LIBRARY_PATH=$(LD_LIBRARY_PATH) \
                 PATH=$(SVN_PREFIX)/bin:$$PATH \
- $(LIB_PTHREAD_HACK) \
- env MAKEFLAGS= make check-swig-rb 2>&1) | \
+ MAKEFLAGS= make check-swig-rb 2>&1) | \
                         tee $(svn_builddir)/tests.log.bindings.rb
 
 svn-check-javahl:

------------------------------------------------------------------------
Received on 2018-02-12 13:08:09 CET

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