*** This bug is a security vulnerability ***
Private security bug reported:
In order to address variant 3 on IBM POWER systems we must flush
the L1D cache on return from exceptions into userspace. We do this
by leveraging conveniently newly added nop space instructions that
have the effect of guaranteeing a given kernel VA is not present
in the L1 cache upon return to user (on POWER, such loads can only
happen explicitly under kernel control, so this is an alternative
to the KAISER/KPTI patches for this architecture). The new feature
is known as "rfi_flush" and is runtime controllable via sysfs.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage)
Status: New
** Tags: architecture-ppc64le bugnameltc-163123 severity-critical
targetmilestone-inin1710
** Tags added: architecture-ppc64le bugnameltc-163123 severity-critical
targetmilestone-inin1710
** Changed in: ubuntu
Assignee: (unassigned) => Ubuntu on IBM Power Systems Bug Triage
(ubuntu-power-triage)
** Package changed: ubuntu => linux (Ubuntu)
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https://bugs.launchpad.net/bugs/1741497
Title:
powerpc: flush L1D on return to use
Status in linux package in Ubuntu:
New
Bug description:
In order to address variant 3 on IBM POWER systems we must flush
the L1D cache on return from exceptions into userspace. We do this
by leveraging conveniently newly added nop space instructions that
have the effect of guaranteeing a given kernel VA is not present
in the L1 cache upon return to user (on POWER, such loads can only
happen explicitly under kernel control, so this is an alternative
to the KAISER/KPTI patches for this architecture). The new feature
is known as "rfi_flush" and is runtime controllable via sysfs.
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