linux-stable.git/Documentation/admin-guide, branch v4.14.91

x86/speculation: Provide IBPB always command line options

2018-12-05T18:41:22+00:00

commit 55a974021ec952ee460dc31ca08722158639de72 upstream

Provide the possibility to enable IBPB always in combination with 'prctl'
and 'seccomp'.

Add the extra command line options and rework the IBPB selection to
evaluate the command instead of the mode selected by the STIPB switch case.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185006.144047038@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-05T18:41:22+00:00

commit 6b3e64c237c072797a9ec918654a60e3a46488e2 upstream

If 'prctl' mode of user space protection from spectre v2 is selected
on the kernel command-line, STIBP and IBPB are applied on tasks which
restrict their indirect branch speculation via prctl.

SECCOMP enables the SSBD mitigation for sandboxed tasks already, so it
makes sense to prevent spectre v2 user space to user space attacks as
well.

The Intel mitigation guide documents how STIPB works:
    
   Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor
   prevents the predicted targets of indirect branches on any logical
   processor of that core from being controlled by software that executes
   (or executed previously) on another logical processor of the same core.

Ergo setting STIBP protects the task itself from being attacked from a task
running on a different hyper-thread and protects the tasks running on
different hyper-threads from being attacked.

While the document suggests that the branch predictors are shielded between
the logical processors, the observed performance regressions suggest that
STIBP simply disables the branch predictor more or less completely. Of
course the document wording is vague, but the fact that there is also no
requirement for issuing IBPB when STIBP is used points clearly in that
direction. The kernel still issues IBPB even when STIBP is used until Intel
clarifies the whole mechanism.

IBPB is issued when the task switches out, so malicious sandbox code cannot
mistrain the branch predictor for the next user space task on the same
logical processor.

Signed-off-by: Jiri Kosina 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185006.051663132@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Enable prctl mode for spectre_v2_user

2018-12-05T18:41:22+00:00

commit 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 upstream

Now that all prerequisites are in place:

 - Add the prctl command line option

 - Default the 'auto' mode to 'prctl'

 - When SMT state changes, update the static key which controls the
   conditional STIBP evaluation on context switch.

 - At init update the static key which controls the conditional IBPB
   evaluation on context switch.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.958421388@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add command line control for indirect branch speculation

2018-12-05T18:41:21+00:00

commit fa1202ef224391b6f5b26cdd44cc50495e8fab54 upstream

Add command line control for user space indirect branch speculation
mitigations. The new option is: spectre_v2_user=

The initial options are:

    -  on:   Unconditionally enabled
    - off:   Unconditionally disabled
    -auto:   Kernel selects mitigation (default off for now)

When the spectre_v2= command line argument is either 'on' or 'off' this
implies that the application to application control follows that state even
if a contradicting spectre_v2_user= argument is supplied.

Originally-by: Tim Chen 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.082720373@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/earlyprintk: Add a force option for pciserial device

2018-11-27T15:10:47+00:00

[ Upstream commit d2266bbfa9e3e32e3b642965088ca461bd24a94f ]

The "pciserial" earlyprintk variant helps much on many modern x86
platforms, but unfortunately there are still some platforms with PCI
UART devices which have the wrong PCI class code. In that case, the
current class code check does not allow for them to be used for logging.

Add a sub-option "force" which overrides the class code check and thus
the use of such device can be enforced.

 [ bp: massage formulations. ]

Suggested-by: Borislav Petkov 
Signed-off-by: Feng Tang 
Signed-off-by: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: "Stuart R . Anderson" 
Cc: Bjorn Helgaas 
Cc: David Rientjes 
Cc: Feng Tang 
Cc: Frederic Weisbecker 
Cc: Greg Kroah-Hartman 
Cc: H Peter Anvin 
Cc: Ingo Molnar 
Cc: Jiri Kosina 
Cc: Jonathan Corbet 
Cc: Kai-Heng Feng 
Cc: Kate Stewart 
Cc: Konrad Rzeszutek Wilk 
Cc: Peter Zijlstra 
Cc: Philippe Ombredanne 
Cc: Thomas Gleixner 
Cc: Thymo van Beers 
Cc: alan@linux.intel.com
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/20181002164921.25833-1-feng.tang@intel.com
Signed-off-by: Sasha Levin

KVM: VMX: Tell the nested hypervisor to skip L1D flush on vmentry

2018-08-15T16:13:00+00:00

commit 5b76a3cff011df2dcb6186c965a2e4d809a05ad4 upstream

When nested virtualization is in use, VMENTER operations from the nested
hypervisor into the nested guest will always be processed by the bare metal
hypervisor, and KVM's "conditional cache flushes" mode in particular does a
flush on nested vmentry.  Therefore, include the "skip L1D flush on
vmentry" bit in KVM's suggested ARCH_CAPABILITIES setting.

Add the relevant Documentation.

Signed-off-by: Paolo Bonzini 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

Documentation/l1tf: Remove Yonah processors from not vulnerable list

2018-08-15T16:12:59+00:00

commit 58331136136935c631c2b5f06daf4c3006416e91 upstream

Dave reported, that it's not confirmed that Yonah processors are
unaffected. Remove them from the list.

Reported-by: ave Hansen 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

Documentation/l1tf: Fix typos

2018-08-15T16:12:57+00:00

commit 1949f9f49792d65dba2090edddbe36a5f02e3ba3 upstream

Fix spelling and other typos

Signed-off-by: Tony Luck 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

Documentation: Add section about CPU vulnerabilities

2018-08-15T16:12:56+00:00

commit 3ec8ce5d866ec6a08a9cfab82b62acf4a830b35f upstream

Add documentation for the L1TF vulnerability and the mitigation mechanisms:

  - Explain the problem and risks
  - Document the mitigation mechanisms
  - Document the command line controls
  - Document the sysfs files

Signed-off-by: Thomas Gleixner 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Josh Poimboeuf 
Acked-by: Linus Torvalds 
Link: https://lkml.kernel.org/r/20180713142323.287429944@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/bugs, kvm: Introduce boot-time control of L1TF mitigations

2018-08-15T16:12:56+00:00

commit d90a7a0ec83fb86622cd7dae23255d3c50a99ec8 upstream

Introduce the 'l1tf=' kernel command line option to allow for boot-time
switching of mitigation that is used on processors affected by L1TF.

The possible values are:

  full
	Provides all available mitigations for the L1TF vulnerability. Disables
	SMT and enables all mitigations in the hypervisors. SMT control via
	/sys/devices/system/cpu/smt/control is still possible after boot.
	Hypervisors will issue a warning when the first VM is started in
	a potentially insecure configuration, i.e. SMT enabled or L1D flush
	disabled.

  full,force
	Same as 'full', but disables SMT control. Implies the 'nosmt=force'
	command line option. sysfs control of SMT and the hypervisor flush
	control is disabled.

  flush
	Leaves SMT enabled and enables the conditional hypervisor mitigation.
	Hypervisors will issue a warning when the first VM is started in a
	potentially insecure configuration, i.e. SMT enabled or L1D flush
	disabled.

  flush,nosmt
	Disables SMT and enables the conditional hypervisor mitigation. SMT
	control via /sys/devices/system/cpu/smt/control is still possible
	after boot. If SMT is reenabled or flushing disabled at runtime
	hypervisors will issue a warning.

  flush,nowarn
	Same as 'flush', but hypervisors will not warn when
	a VM is started in a potentially insecure configuration.

  off
	Disables hypervisor mitigations and doesn't emit any warnings.

Default is 'flush'.

Let KVM adhere to these semantics, which means:

  - 'lt1f=full,force'	: Performe L1D flushes. No runtime control
    			  possible.

  - 'l1tf=full'
  - 'l1tf-flush'
  - 'l1tf=flush,nosmt'	: Perform L1D flushes and warn on VM start if
			  SMT has been runtime enabled or L1D flushing
			  has been run-time enabled

  - 'l1tf=flush,nowarn'	: Perform L1D flushes and no warnings are emitted.

  - 'l1tf=off'		: L1D flushes are not performed and no warnings
			  are emitted.

KVM can always override the L1D flushing behavior using its 'vmentry_l1d_flush'
module parameter except when lt1f=full,force is set.

This makes KVM's private 'nosmt' option redundant, and as it is a bit
non-systematic anyway (this is something to control globally, not on
hypervisor level), remove that option.

Add the missing Documentation entry for the l1tf vulnerability sysfs file
while at it.

Signed-off-by: Jiri Kosina 
Signed-off-by: Thomas Gleixner 
Tested-by: Jiri Kosina 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Josh Poimboeuf 
Link: https://lkml.kernel.org/r/20180713142323.202758176@linutronix.de
Signed-off-by: Greg Kroah-Hartman