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[Robert Ancell <robert.ancell@xxxxxxxxxxxxx>]

The way I found this was by testing the SRU in vivid - for some reason
the X server was sending Request packets with a addresses field empty.
Other Ubuntu releases are not doing this. I haven't yet investigated if
why it was doing this.

** Also affects: lightdm (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: lightdm (Ubuntu Wily)
   Importance: Undecided
       Status: New

** Changed in: lightdm (Ubuntu)
       Status: New => Fix Committed

** Changed in: lightdm (Ubuntu Wily)
       Status: New => Fix Committed

** Changed in: lightdm (Ubuntu)
   Importance: Undecided => Critical

** Changed in: lightdm (Ubuntu Wily)
   Importance: Undecided => Critical

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https://bugs.launchpad.net/bugs/1516831

Title:
  XDMCP Request packet with no addresses crashes LightDM

Status in Light Display Manager:
  Fix Released
Status in Light Display Manager 1.14 series:
  Fix Released
Status in Light Display Manager 1.16 series:
  Fix Released
Status in lightdm package in Ubuntu:
  Fix Committed
Status in lightdm source package in Wily:
  Fix Committed

Bug description:
  [Impact]
  If LightDM receives an XDMCP Request packet with no addresses then it will attempt to access a negative index into an array and crash. This only occurs if the XDMCP server is enabled.

  [Test Case]
  1. Enable XDMCP in lightdm.conf:
  [XDMCPServer]
  enabled=true
  2. Start LightDM
  3. Send an XDMCP Request without an empty addresses field (valid XDMCP servers do not send this).

  Expected result:
  The request is ignored.

  Observed result:
  LightDM crashes.

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