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SubjectRe: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes
On Sat, 17 Nov 2018, Jiri Kosina wrote:

> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 81d1d5a..9c306e3 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -4215,6 +4215,26 @@
> > Not specifying this option is equivalent to
> > spectre_v2=auto.
> >
> > + spectre_v2_app2app=
> > + [X86] Control mitigation of Spectre variant 2
> > + application to application (indirect branch speculation)
> > + vulnerability.
> > +
> > + off - Unconditionally disable mitigations
> > + lite - Protect tasks which have requested restricted
> > + indirect branch speculation via the
> > + PR_SET_SPECULATION_CTRL prctl().
>
> Don't we also want to do the same for SECCOMP processess, analogically how
> we do it for SSBD?

IOW, how about patch below on top of your series? Thanks.


From: Jiri Kosina <jkosina@suse.cz>
Subject: [PATCH] x86/speculation: enforce STIBP for SECCOMP tasks in lite mode

If 'lite' mode of app2app protection from spectre_v2 is selected on
kernel command-line, we are currently applying STIBP protection to
non-dumpable tasks, and tasks that have explicitly requested such
protection via

prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0);

Let's extend this to cover also SECCOMP tasks (analogically to how we
apply SSBD protection).

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
Documentation/admin-guide/kernel-parameters.txt | 9 +++++----
arch/x86/kernel/cpu/bugs.c | 2 ++
2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 102f9a169eec..74f547e5c8f6 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4221,10 +4221,11 @@
vulnerability.

off - Unconditionally disable mitigations
- lite - Protect tasks which are marked non-dumpable
- and tasks which have requested restricted
- indirect branch speculation via the
- PR_SET_SPECULATION_CTRL prctl().
+ lite - Protect tasks which are marked non-dumpable,
+ tasks which have requested restricted indirect
+ branch speculation via the
+ PR_SET_SPECULATION_CTRL prctl() and seccomp
+ tasks.
strict - Protect all processes
auto - Kernel selects the mode

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e7f9334f18c0..3ec952108e87 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -863,6 +863,8 @@ void arch_seccomp_spec_mitigate(struct task_struct *task)
{
if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
+ if (spectre_v2_app2app_enabled == SPECTRE_V2_APP2APP_LITE)
+ set_task_stibp(task, true);
}
#endif

--
Jiri Kosina
SUSE Labs

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