[V32,19/27] x86/mmiotrace: Lock down the testmmiotrace module

Commit Message

Matthew Garrett April 4, 2019, 12:32 a.m. UTC

From: David Howells <[e-mail]>

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 <[e-mail]>
Signed-off-by: David Howells <[e-mail]
Signed-off-by: Matthew Garrett <[e-mail]>
cc: Thomas Gleixner <[e-mail]>
cc: Steven Rostedt <[e-mail]>
cc: Ingo Molnar <[e-mail]>
cc: "H. Peter Anvin" <[e-mail]>
cc: [e-mail]
---
 arch/x86/mm/testmmiotrace.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Steven Rostedt April 4, 2019, 1:33 a.m. UTC | #1

On Wed,  3 Apr 2019 17:32:41 -0700
Matthew Garrett <[e-mail]> wrote:

> From: David Howells <[e-mail]>
> 
> 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 <[e-mail]>
> Signed-off-by: David Howells <[e-mail]
> Signed-off-by: Matthew Garrett <[e-mail]>
> cc: Thomas Gleixner <[e-mail]>
> cc: Steven Rostedt <[e-mail]>

Acked-by: Steven Rostedt (VMware) <[e-mail]>

-- Steve

> cc: Ingo Molnar <[e-mail]>
> cc: "H. Peter Anvin" <[e-mail]>
> cc: [e-mail]
> ---
>  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");

Thomas Gleixner April 4, 2019, 7:47 a.m. UTC | #2

On Wed, 3 Apr 2019, Matthew Garrett wrote:

> From: David Howells <[e-mail]>
> 
> 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 <[e-mail]>
> Signed-off-by: David Howells <[e-mail]
> Signed-off-by: Matthew Garrett <[e-mail]>

Reviewed-by: Thomas Gleixner <[e-mail]>

Patch

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");