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SubjectRe: [Patch v2 4/4] x86/speculation: Add prctl to control indirect branch speculation per process

* Tim Chen <tim.c.chen@linux.intel.com> wrote:

> To migitgate possible app to app attack from branch target buffer poisoning,
> a new prctl is provided to control branch speculation for applications in
> user app. The following interfaces are provided:

s/migitgate
/mitigate

>
> prctl(PR_SET_SPECULATION_CTRL, PR_INDIR_BRANCH, PR_SPEC_DISABLE, 0, 0);
> - Disable branch target speculation to protect against app to app
> style attack using IBPB and STIBP
>
> prctl(PR_SET_SPECULATION_CTRL, PR_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0);
> - Allow branch target speculation, no mitigation for Spectre V2
>
> prctl(PR_GET_SPECULATION_CTRL, PR_INDIR_BRANCH, 0, 0, 0)
> - Query the indirect branch speculation restriction on a process

Well 'a process' is always 'the current process' in this case, right?

> - lite - only turn on mitigation for non-dumpable processes
> + lite - turn on mitigation for non-dumpable processes
> + or processes that has indirect branch restricted
> + via prctl's PR_SET_SPECULATION_CTRL option

s/or processes that has indirect
/or processes that have been indirect

?

> + /*
> + * If being set on non-current task, delay setting the CPU
> + * mitigation until it is next scheduled.
> + * Use speculative_store_bypass_update will update SPEC_CTRL MSR
> + */
> + if (task == current && update)
> + speculative_store_bypass_update_current();

Did you mean:

Call to speculative_store_bypass_update_current() will update SPEC_CTRL MSR

?


> - * For lite protection mode, we only protect the non-dumpable
> - * processes.
> + * For lite protection mode, we protect processes
> + * where the user explicitly disable indirect branch
> + * speculation or mark the process as non-dumpable.

s/where the user explicitly disable
/where the user explicitly disables

?

Thanks,

Ingo

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