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[Launchpad Bug Tracker <1388952@xxxxxxxxxxxxxxxxxx>]

** Branch linked: lp:ubuntu/trusty-proposed/linux-keystone

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https://bugs.launchpad.net/bugs/1388952

Title:
  CONFIG_IPMI_SI_PROBE_DEFAULTS should be disabled on ARM

Status in “linux” package in Ubuntu:
  Fix Committed
Status in “linux” source package in Trusty:
  Fix Committed
Status in “linux” source package in Utopic:
  Fix Committed
Status in “linux” source package in Vivid:
  Fix Committed

Bug description:
  [Impact]
  Causes fault which can lead to a hang or crash on ARM systems when loading the ipmi_si module.

  The ipmi_si driver includes code that probes into iospace for a KCS
  interface. This is to support platforms that don't expose this
  interface in SMBIOS/ACPI tables, and this is a defined discovery
  mechanism as per the IPMI Spec (v2.0r1, section 9.5).  However, this
  assumption is x86-centric. It is not safe to blindly probe I/O space
  on ARM platforms.

  [Test Case]
  sudo modprobe ipmi_si

  This should discover an IPMI system interface if present, or fail to
  load otherwise. But it should not cause a hang, a synchronous external
  abort, or other kernel failure.

  [Regression Risk]
  The proposed fix is only to the ARM config, so the risk to other architectures is negligible. There is a risk that there exists some system out there where this probing works - but I'm highly confident no such system exists. Existing ARM systems supported by Ubuntu either describe their IPMI/KCS interface using device-tree or do not provide one.

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