kernel-packages team mailing list archive

[Philipp Kern <phil+launchpad@xxxxxxxxxxx>]

Trying to kexec with the sysctl enabled correctly gives "kexec_load
failed: Operation not permitted". Re-enabling it does not work, as
expected. With the sysctl untouched kexec works just fine.

** Tags removed: verification-needed-saucy
** Tags added: verification-done-saucy

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https://bugs.launchpad.net/bugs/1259570

Title:
  kexec should get a disabling sysctl

Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux-lts-saucy” package in Ubuntu:
  Invalid
Status in “linux” source package in Precise:
  Won't Fix
Status in “linux-lts-saucy” source package in Precise:
  Fix Committed
Status in “linux” source package in Quantal:
  Won't Fix
Status in “linux-lts-saucy” source package in Quantal:
  Invalid
Status in “linux” source package in Raring:
  Invalid
Status in “linux-lts-saucy” source package in Raring:
  Invalid
Status in “linux” source package in Saucy:
  Fix Committed
Status in “linux-lts-saucy” source package in Saucy:
  Invalid
Status in “linux” source package in Trusty:
  Fix Released
Status in “linux-lts-saucy” source package in Trusty:
  Invalid

Bug description:
  To enable kexec makes sense for a generic distro kernel. But if your
  users have root in their virtual machines, and you want to make it
  hard for them to run code in ring 0, you commonly disable further
  module loading and you also want to disable kexec[1]. Kees Cook wrote
  up a patch[2] that we'd like to see applied to the Ubuntu kernel to
  avoid recompilation of the distro kernel.

  I'm marking this as a security issue on the ground that it's quite
  surprising that setting kernel.modules_disabled=1 as a hardening
  feature can be subverted by using kexec.

  [1] http://mjg59.dreamwidth.org/28746.html
  [2] https://lkml.org/lkml/2013/12/9/765

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