Re: [Patch v7 14/18] x86/speculation: Add 'seccomp' Spectre v2 app to app protection mode

[Tim Chen <tim.c.chen@linux.intel.com>]

On 11/20/2018 04:08 PM, Tim Chen wrote:

> From: Jiri Kosina <jkosina@suse.cz>
> 
> If 'prctl' mode of app2app protection from spectre_v2 is selected on
> kernel command-line, we are currently applying STIBP protection to
> tasks that restrict their indirect branch speculation 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).
> 
> According to software guidance:
> 
> "Setting ... STIBP ... 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."
> 
> https://software.intel.com/security-software-guidance/insights/deep-dive-single-thread-indirect-branch-predictors
> 
> Hence setting STIBP on a sandboxed task will prevent the task
> from attacking other sibling threads or getting attacked.
> 
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> ---

Will need this chunk added, which I missed in my update of Jiri's patch.

Thanks.

Tim

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c4d010d..d070e84 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -275,6 +275,7 @@ enum spectre_v2_app2app_cmd {
 	{ "off",	SPECTRE_V2_APP2APP_CMD_NONE,	false },
 	{ "on",		SPECTRE_V2_APP2APP_CMD_FORCE,	true  },
 	{ "prctl",	SPECTRE_V2_APP2APP_CMD_PRCTL,	false },
+	{ "seccomp",	SPECTRE_V2_APP2APP_CMD_SECCOMP,	false },
 };
 
 static void __init spec_v2_app_print_cond(const char *reason, bool secure)