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x86/speculation: Make "seccomp" the default mode for Speculative Store Bypass

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Unless explicitly opted out of, anything running under seccomp will have
SSB mitigations enabled. Choosing the "prctl" mode will disable this.

[ tglx: Adjusted it to the new arch_seccomp_spec_mitigate() mechanism ]

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Kees Cook
2018-05-03 14:37:54 -07:00
committed by Thomas Gleixner
parent 8bf37d8c06
commit f21b53b20c
3 changed files with 41 additions and 18 deletions
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26
Documentation/admin-guide/kernel-parameters.txt
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@@ -4049,19 +4049,27 @@
This parameter controls whether the Speculative Store
Bypass optimization is used.
on - Unconditionally disable Speculative Store Bypass
off - Unconditionally enable Speculative Store Bypass
auto - Kernel detects whether the CPU model contains an
implementation of Speculative Store Bypass and
picks the most appropriate mitigation.
prctl - Control Speculative Store Bypass per thread
via prctl. Speculative Store Bypass is enabled
for a process by default. The state of the control
is inherited on fork.
on - Unconditionally disable Speculative Store Bypass
off - Unconditionally enable Speculative Store Bypass
auto - Kernel detects whether the CPU model contains an
implementation of Speculative Store Bypass and
picks the most appropriate mitigation. If the
CPU is not vulnerable, "off" is selected. If the
CPU is vulnerable the default mitigation is
architecture and Kconfig dependent. See below.
prctl - Control Speculative Store Bypass per thread
via prctl. Speculative Store Bypass is enabled
for a process by default. The state of the control
is inherited on fork.
seccomp - Same as "prctl" above, but all seccomp threads
will disable SSB unless they explicitly opt out.
Not specifying this option is equivalent to
spec_store_bypass_disable=auto.
Default mitigations:
X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
spia_io_base= [HW,MTD]
spia_fio_base=
spia_pedr=