perl client crash after timeout while connecting

[Brad Fitzpatrick]

Nice!  :)


On Tue, 3 Jul 2007, Jacques Caron wrote:

> Hi Brad,
>
> FYI, the problem is in the "orassign" (||=) implementation, it breaks
> if you take the left hand side expression "away" while evaluating the
> right hand side. In this case, the problem lies in sock_to_host doing
> a @buck2sock = (). The ||= will have some kind of pointer on
> $buck2sock[$bucket] before calling sock_to_host, which will delete
> it. And perl ends up copying some random crap into an SV, and it
> (usually) breaks a bit later. Perl 5.9.4 at least recognizes it's
> doing something bad, but still doesn't do the right thing.
>
> Got lost in the perl source, so can't yet provide a fix :-( I can
> provide a good test case, though:
>
> my @array;
>
> sub fn
> {
>          @array = ();
> }
>
> $array[0]       =       1;
>
> my $var =       $array[1] ||= fn();
>
> Jacques.
>
> At 00:00 03/07/2007, Brad Fitzpatrick wrote:
> >Crazy.
> >
> >Patch applied.  I'll try to contact Perl people who can look into this bug
> >in Perl.
> >
> >- Brad
> >
> >
> >On Thu, 28 Jun 2007, Matthieu PATOU wrote:
> >
> > > Dear list
> > > the current version (1.23 from SVN) of the memcached perl client
> > crash when it once fail to connect an host and the
> > > success to connect to another host.
> > >
> > > On my workstation (Linux ubuntu 6.10), when the problem occurs i get :
> > >
> > > mat at hades:~/work/memcached-ref/api/perl$ perl mctest.pl
> > > using parser: Cache::Memcached::GetParser
> > > *** glibc detected *** perl: munmap_chunk(): invalid pointer:
> > 0x081fd690 ***
> > > ======= Backtrace: =========
> > > /lib/tls/i686/cmov/libc.so.6(__libc_free+0x18a)[0xb7e02b4a]
> > > perl(Perl_sv_setsv_flags+0x5cb)[0x80d370f]
> > > perl(Perl_pp_sassign+0x56)[0x80c37e4]
> > > perl(Perl_runops_standard+0x13)[0x80bb273]
> > > perl(perl_run+0x2e1)[0x80639b4]
> > > perl(main+0x112)[0x8060012]
> > > /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xdc)[0xb7db18cc]
> > > perl[0x805fe81]
> > > ======= Memory map: ========
> > >
> > >
> > > The GetParserXS module is NOT installed
> > > After some sessions of debugging it appears that it is Perl which
> > fools itself when executing :
> > >    $sock = $buck2sock[$bucket] ||=
> > $self->sock_to_host($self->{buckets}[ $bucket ]
> > >
> > > When sock_to_host had returned undef (because it had been unable
> > to connect to the desired server), the next execution
> > > of this line will crash when trying to set the return value of
> > sock_to_host into $buck2sock[$bucket]
> > >
> > > The test case is in the mctest.pl (I simulate the timeout on
> > connect by NOT having a memcache server listening on 11212).
> > >
> > > I fix the bug by simplifying the code and splitting into smaller
> > pieces (see the patch attached to this mail).
> > >
> > > Cheers
> > > Matthieu
> > >
> > >
> > >
>
>