# Re: \[PATCH 02/27\] Add a SysRq option to lift kernel lockdown

- From: David Howells \<dhowells@redhat.com\>
- Date: 2019-03-07 15:59:39 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/2019/03/5532635
- Thread: https://ratatoskr.run/linux-security-module/2019/03/5532057/t.md

```text
Matthew Garrett [ref] wrote:

> +		/* Ban synthetic events from some sysrq functionality */
> +		if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
> +		    op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
> +			printk("This sysrq operation is disabled from userspace.\n");
>  		/*
>  		 * Should we check for enabled operations (/proc/sysrq-trigger
>  		 * should not) and is the invoked operation enabled?
>  		 */
> -		if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
> +		if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {

There's some missing logic here.  Probably an else is missing, but it seems
more than that.

David
```