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

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Date:   Tue, 07 Nov 2017 15:39:06 -0200
From:   Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-security-module@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
        linux-efi@...r.kernel.org, matthew.garrett@...ula.com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        jforbes@...hat.com
Subject: Re: [PATCH 02/27] Add a SysRq option to lift kernel lockdown


Hello David,

David Howells <dhowells@...hat.com> writes:
> +static struct sysrq_key_op lockdown_lift_sysrq_op = {
> +	.handler	= sysrq_handle_lockdown_lift,
> +	.help_msg	= "unSB(x)",
> +	.action_msg	= "Disabling Secure Boot restrictions",
> +	.enable_mask	= SYSRQ_DISABLE_USERSPACE,
> +};
> +
> +static int __init lockdown_lift_sysrq(void)
> +{
> +	if (kernel_locked_down) {
> +		lockdown_lift_sysrq_op.help_msg[5] = LOCKDOWN_LIFT_KEY;
> +		register_sysrq_key(LOCKDOWN_LIFT_KEY, &lockdown_lift_sysrq_op);
> +	}
> +	return 0;
> +}
> +
> +late_initcall(lockdown_lift_sysrq);
> +
> +#endif /* CONFIG_ALLOW_LOCKDOWN_LIFT_BY_KEY */

On non-x86 platforms (tested on powerpc) this fails to build with:

security/lock_down.c: In function ‘lockdown_lift_sysrq’:
security/lock_down.c:100:40: error: ‘LOCKDOWN_LIFT_KEY’ undeclared (first use in this function)
   lockdown_lift_sysrq_op.help_msg[5] = LOCKDOWN_LIFT_KEY;
                                        ^~~~~~~~~~~~~~~~~
security/lock_down.c:100:40: note: each undeclared identifier is reported only once for each function it appears in

-- 
Thiago Jung Bauermann
IBM Linux Technology Center