Bug #4409

DRb: discrepency between DRb.here? and DRb.uri leads to failure to dereference a DrbObject

Added by Nicolas Bondoux over 4 years ago. Updated almost 4 years ago.

Assignee:Masatoshi Seki
ruby -v:ruby 1.9.2p0 (2010-08-18 revision 29036) [i486-linux] Backport:


When a reference on a local object is sent back by a client to a server, it may not be recognised as a local object during marshalling:
An object instance being sent as a reference is wrapped in a DRbObject built by make_proxy with DRbObject.new(obj); the DRbObject's uri will be the uri returned by DRb::uri.
When this reference is sent back, DRbObject::_load checks if it matches uri of current server with DRb::here? method.

The problem is that DRb.here? checks that a DRbObject uri is the same as the uri which was used by current DRbServer at his creation, while DRb.uri will return an uri created from the local socket from current thread's connection.

So, when a DRbObject it sent back, it may not be recognized as referencing a local object

Fixing DRb.here? so that it compares with the uri returned by DRb.uri should be enough to quick fix this problem, and seems safe to me.
(I call it a quick fix because I am sure that even with this change, it is possible to build some less realistics cases with the same kind of problem, due to the fact that a same reference may be valid or not depending which client sent it back ...)

Here is a very simple proof of concept:
The server:

require 'drb'
class A
include DRb::DRbUndumped

class TheServer
include DRb::DRbUndumped
def initialize
@a = A.new

def get_a

def is_a(iA)
puts "inside is_a: current DRb.uri:#{DRb.uri}; iA.class = #{iA.class} #{iA.__drburi if DRb::DRbObject === iA}"
@a.eql? iA

def getToken
retVal = @@token.clone
return retVal


theServer = TheServer.new
puts "DRb.uri just after start_service: #{DRb.uri}"

The client:

require 'drb'

theServer = DRb::DRbObject.new(nil,ARGV.shift)

a = theServer.get_a
puts "a.drburi == #{a.drburi}"
puts "theServer.is_a(a) == #{theServer.is_a(a)}"

the outputs:
server side:
DRb.uri just after start_service: druby://Venus:60106
inside is_a: current DRb.uri:druby://; iA.class = DRb::DRbObject druby://

client side:
a._drburi == druby://
a(a) == false



Associated revisions

Revision 32254
Added by Masatoshi Seki over 4 years ago

fix [Bug #4409]. add DRbServer#here?

Revision 32254
Added by Masatoshi Seki over 4 years ago

fix [Bug #4409]. add DRbServer#here?


#1 Updated by Yui NARUSE over 4 years ago

  • Status changed from Open to Assigned
  • Assignee set to Masatoshi Seki

#2 Updated by Hiroshi Nakamura over 4 years ago

  • Target version set to 1.9.3

#3 Updated by Masatoshi Seki over 4 years ago

  • Status changed from Assigned to Closed
  • % Done changed from 0 to 100

This issue was solved with changeset r32254.
Nicolas, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

fix [Bug #4409]. add DRbServer#here?

#4 Updated by Cory Banks almost 4 years ago

Nicolas, thank you for reporting this issue - http://roofracksforvan.com

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