| Subject: | Partial MessagePack can cause a memory leak via Data::MessagePack::Stream |
| Date: | Mon, 11 Jun 2018 22:37:42 +0300 |
| To: | bug-Data-MessagePack-Stream [...] rt.cpan.org |
| From: | msigurko <m.sigor [...] gmail.com> |
Hello,
Please consider the short script below, that demonstrates a memory leak
possibility, in a long lived process.
-----------------------------------------
#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use Data::MessagePack;
use Data::MessagePack::Stream;
my $mp = Data::MessagePack->new;
my $packed_junk = $mp->encode(pack('a*', 'a' x 1024 ));
my $stream = Data::MessagePack::Stream->new;
$stream->feed( $mp->encode('foo') );
$stream->feed( substr($packed_junk, 0, 512) );
$stream->feed( $mp->encode('bar') );
# this prints only 'foo'
while ($stream->next) {
print Dumper($stream->data);
}
print "Nothing more to stream!!\n"; # or is there?
-----------------------------------------
'$stream' hangs on to the partial MP (where we 'feed' a 'substr' of an MP)
it also hangs on to any MP that we 'feed' after that
'$stream->next' returns nothing, thus one may decide that it's empty -
while it is clearly not
While not a bug in MP, however, it is very easy, for an unsuspecting user,
to leak memory via MP, as can be seen above.
For the case where MP is created elsewhere and is then delivered via unsafe
means (socket, file, etc, which may get corrupted along the way) to the
Stream(er) - it is very difficult to diagnose the memory leak caused by
that.
Please consider providing some kind of protection against this use case.
Best,
Matthew.