Re: [mp2] mod_perl 2.0.7 Segfault When Loading Certain Perl Module

Hi once more:

I've installed a mod_perl compiled with MP_DEBUG=1 and obtained a core 
file, from which I get this stack trace when loading Carp.pm.  It seems
it segfaults when compiling the regular expression from this line 
in Carp.pm:

is_utf8($arg) or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;

Does this help at all?

Regards,

   Doug Hunt

-------------------%<--------------------------------------------
(gdb) where
#0  0x0000000000513346 in Perl__invlist_union_maybe_complement_2nd ()
#1  0x000000000051642d in S_regclass ()
#2  0x0000000000518e38 in S_regpiece ()
#3  0x000000000051ab30 in S_regbranch ()
#4  0x000000000051ae2d in S_reg ()
#5  0x0000000000518dae in S_regpiece ()
#6  0x000000000051ab30 in S_regbranch ()
#7  0x000000000051ae2d in S_reg ()
#8  0x000000000051dadc in Perl_re_compile ()
#9  0x00000000004d2d24 in Perl_pmruntime ()
#10 0x0000000000506404 in Perl_yyparse ()
#11 0x00000000005721b0 in S_doeval ()
#12 0x0000000000573ea9 in Perl_pp_require ()
#13 0x0000000000489ee1 in modperl_pp_require ()
#14 0x000000000053fc93 in Perl_runops_standard ()
#15 0x00000000004dd0c3 in Perl_eval_sv ()
#16 0x000000000047c3de in modperl_require_module (pv=0x1b8a498 "Carp", 
logfailure=1)
#17 0x0000000000475e6d in modperl_config_apply_PerlModule (s=0x1b68950, 
scfg=0x1b6ca00, perl=0x1beeb10, p=0x1b5f138)
#18 0x000000000047322f in modperl_startup (s=0x1b68950, p=0x1b5f138)
#19 0x0000000000472ee2 in modperl_startup (s=0x1b68950, p=0x1b5f138)
#20 0x000000000047415b in modperl_init (base_server=0x1b68950, 
p=0x1b5f138)
#21 0x0000000000474484 in modperl_hook_init (pconf=0x1b5f138, 
plog=0x1ba5368, ptemp=0x1b69188, s=0x1b68950)
#22 0x0000000000464701 in ap_run_open_logs ()
#23 0x000000000044abed in main ()
----------------------%<-------------------------------------------------



[email protected]
Software Engineer
UCAR - COSMIC, Tel. (303) 497-2611

On Mon, 20 Aug 2012, Doug Hunt wrote:

> Hi Fred, modperl folks:
>
> We've narrowed down this bug a bit more.  We are currently running perl 
> 5.16.1 (latest), the latest mod_perl from source and apache version 2.2.22.
>
> If we run a simple httpd.conf with this line:
>
> PerlModule Carp
>
> Then single-process startup will fail on the second perl startup.
> (perl starts up twice when apache is started, as explained in 
> http://perl.apache.org/docs/2.0/user/handlers/server.html).
>
> httpd -X
> (segmentation fault)
>
> We can tell that apache starts up perl successfully the first time by running 
> strace.  The segfault can be traced to one line in Carp.pm:
>
> --------------------%<----------------------------------------------------
> # Transform an argument to a function into a string.
> sub format_arg {
>
> ...
>
>    # The following handling of "control chars" is direct from
>    # the original code - it is broken on Unicode though.
>    # Suggestions?
>    is_utf8($arg) or $arg =~ 
> s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
>    return $arg;
> }
> --------------------%<-------------------------------------------------------
>
> If we comment out the line which starts 'is_utf8...' then the segfault is 
> prevented.  It strikes me as odd that just *compiling* that line (which is 
> legal perl) should cause a segfault, but that is what we repeatedly observe.
>
> Any ideas or thoughts welcome!
>
> Regards,
>
>  Doug Hunt
>
> [email protected]
> Software Engineer
> UCAR - COSMIC, Tel. (303) 497-2611
>
> On Tue, 14 Aug 2012, Fred Moyer wrote:
>
>> Can you try the latest version from source?
>> 
>> http://perl.apache.org/download/source.html
>> 
>> It looks like you are using perl 5.16, some recent fixes were
>> committed there. The subversion tip will likely be the 2.0.8 RC in a
>> week or so.
>> 
>> On Mon, Aug 13, 2012 at 3:01 PM, Jason Lin <[email protected]> wrote:
>>> Hi,
>>> 
>>> I work for a project that has been using mod_perl for quite a while.
>>> Recently, we upgraded our 64-bit web server with Perl 5.16, mod_perl 2.0.7
>>> (it's 2.0.6 with patch), and apache 2.2.22 on CentOS 6.3. Since then, 
>>> we've
>>> been unable to start Apache server (segmentation faults) with same
>>> httpd.conf which worked previously.
>>> 
>>> As far as I can tell, the segfault seems to be triggered while trying to
>>> load any Perl module using either PerlModule directive or in <Perl> block 
>>> in
>>> httpd.conf that directly or indirectly use Carp, or even just try to load
>>> Carp itself. Strace shows that the process would segfault while loading 
>>> (or
>>> right after loading) Carp.pm. The server can still successfully start and
>>> work when carefully removing such modules in httpd.conf.
>>> 
>>> Is anyone seeing this same issue or have any ideas how it can be fixed 
>>> other
>>> than trying to hack through all the Perl modules to make sure Carp is not
>>> called?
>>> 
>>> 
>>> perl -V
>>> Summary of my perl5 (revision 5 version 16 subversion 0) configuration:
>>>
>>>   Platform:
>>>     osname=linux, osvers=2.6.32-279.1.1.el6.x86_64, archname=x86_64-linux
>>>     uname='linux fox.cosmic.ucar.edu 2.6.32-279.1.1.el6.x86_64 #1 smp tue
>>> jul 10 13:47:21 utc 2012 x86_64 x86_64 x86_64 gnulinux '
>>>     config_args='-Dprefix=/ops/tools -des
>>> -Accflags=-DPERL_RELOCATABLE_INCPUSH'
>>>     hint=recommended, useposix=true, d_sigaction=define
>>>     useithreads=undef, usemultiplicity=undef
>>>     useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
>>>     use64bitint=define, use64bitall=define, uselongdouble=undef
>>>     usemymalloc=n, bincompat5005=undef
>>>   Compiler:
>>>     cc='cc', ccflags ='-DPERL_RELOCATABLE_INCPUSH -fno-strict-aliasing 
>>> -pipe
>>> -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE
>>> -D_FILE_OFFSET_BITS=64',
>>>     optimize='-O2',
>>>     cppflags='-DPERL_RELOCATABLE_INCPUSH -fno-strict-aliasing -pipe
>>> -fstack-protector -I/usr/local/include'
>>>     ccversion='', gccversion='4.4.6 20120305 (Red Hat 4.4.6-4)',
>>> gccosandvers=''
>>>     intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
>>>     d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
>>>     ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
>>> lseeksize=8
>>>     alignbytes=8, prototype=define
>>>   Linker and Libraries:
>>>     ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
>>>     libpth=/usr/local/lib /lib/../lib64 /usr/lib/../lib64 /lib /usr/lib
>>> /lib64 /usr/lib64 /usr/local/lib64
>>>     libs=-lnsl -lgdbm -ldl -lm -lcrypt -lutil -lc
>>>     perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
>>>     libc=, so=so, useshrplib=false, libperl=libperl.a
>>>     gnulibc_version='2.12'
>>>   Dynamic Linking:
>>>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
>>>     cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib
>>> -fstack-protector'
>>> 
>>> 
>>> Characteristics of this binary (from libperl):
>>>   Compile-time options: HAS_TIMES PERLIO_LAYERS PERL_DONT_CREATE_GVSV
>>>                         PERL_MALLOC_WRAP PERL_PRESERVE_IVUV
>>>                         PERL_RELOCATABLE_INCPUSH USE_64_BIT_ALL
>>>                         USE_64_BIT_INT USE_LARGE_FILES USE_LOCALE
>>>                         USE_LOCALE_COLLATE USE_LOCALE_CTYPE
>>>                         USE_LOCALE_NUMERIC USE_PERLIO USE_PERL_ATOF
>>>   Built under linux
>>>   Compiled at Aug  1 2012 16:14:39
>>>   %ENV:
>>>     PERL5LIB="/ops/tools/lib"
>>>   @INC:
>>>     /ops/tools/lib
>>>     /ops/tools/lib/perl5/site_perl/5.16.0/x86_64-linux
>>>     /ops/tools/lib/perl5/site_perl/5.16.0
>>>     /ops/tools/lib/perl5/5.16.0/x86_64-linux
>>>     /ops/tools/lib/perl5/5.16.0
>>>     .
>>> 
>>> Note that we compiled Perl with relocation flag 
>>> (-DPERL_RELOCATABLE_INCPUSH)
>>> turned on, yet same issue can also be found without the flag in our test.
>>> 
>>> Any help/advice would be appreciated, thank you in advance.
>>> 
>>> 
>>> Best,
>>> Jason
>> 
>