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SubjectRe: [PATCH V32 19/27] x86/mmiotrace: Lock down the testmmiotrace module
On Wed,  3 Apr 2019 17:32:41 -0700
Matthew Garrett <matthewgarrett@google.com> wrote:

> From: David Howells <dhowells@redhat.com>
>
> The testmmiotrace module shouldn't be permitted when the kernel is locked
> down as it can be used to arbitrarily read and write MMIO space. This is
> a runtime check rather than buildtime in order to allow configurations
> where the same kernel may be run in both locked down or permissive modes
> depending on local policy.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: David Howells <dhowells@redhat.com
> Signed-off-by: Matthew Garrett <mjg59@google.com>
> cc: Thomas Gleixner <tglx@linutronix.de>
> cc: Steven Rostedt <rostedt@goodmis.org>

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

> cc: Ingo Molnar <mingo@kernel.org>
> cc: "H. Peter Anvin" <hpa@zytor.com>
> cc: x86@kernel.org
> ---
> arch/x86/mm/testmmiotrace.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/mm/testmmiotrace.c b/arch/x86/mm/testmmiotrace.c
> index f6ae6830b341..9e8ad665f354 100644
> --- a/arch/x86/mm/testmmiotrace.c
> +++ b/arch/x86/mm/testmmiotrace.c
> @@ -115,6 +115,9 @@ static int __init init(void)
> {
> unsigned long size = (read_far) ? (8 << 20) : (16 << 10);
>
> + if (kernel_is_locked_down("MMIO trace testing", LOCKDOWN_INTEGRITY))
> + return -EPERM;
> +
> if (mmio_address == 0) {
> pr_err("you have to use the module argument mmio_address.\n");
> pr_err("DO NOT LOAD THIS MODULE UNLESS YOU REALLY KNOW WHAT YOU ARE DOING!\n");

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