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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Nayna Jain <nayna@linux.ibm.com>, linuxppc-dev@ozlabs.org,
        linux-efi@vger.kernel.org, linux-integrity@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Jeremy Kerr <jk@ozlabs.org>,
        Matthew Garret <matthew.garret@nebula.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Claudio Carvalho <cclaudio@linux.ibm.com>,
        George Wilson <gcwilson@linux.ibm.com>,
        Elaine Palmer <erpalmer@us.ibm.com>,
        Eric Ricther <erichte@linux.ibm.com>,
        Oliver O'Halloran <oohall@gmail.com>,
        Nayna Jain <nayna@linux.ibm.com>,
        Prakhar Srivastava <prsriva02@gmail.com>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Subject: Re: [PATCH v8 1/8] powerpc: detect the secure boot mode of the system
In-Reply-To: <1571508377-23603-2-git-send-email-nayna@linux.ibm.com>
References: <1571508377-23603-1-git-send-email-nayna@linux.ibm.com> <1571508377-23603-2-git-send-email-nayna@linux.ibm.com>
Date:   Wed, 23 Oct 2019 10:37:30 +1100
Message-ID: <87zhhs5p39.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Nayna Jain <nayna@linux.ibm.com> writes:
> diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
> new file mode 100644
> index 000000000000..99bba7915629
> --- /dev/null
> +++ b/arch/powerpc/kernel/secure_boot.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +#include <linux/types.h>
> +#include <linux/of.h>
> +#include <asm/secure_boot.h>
> +
> +bool is_ppc_secureboot_enabled(void)
> +{
> +	struct device_node *node;
> +	bool enabled = false;
> +
> +	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-v1");

If this found a node then you have a node with an elevated refcount
which you need to drop on the way out.

> +	if (!of_device_is_available(node)) {
> +		pr_err("Cannot find secure variable node in device tree; failing to secure state\n");
> +		goto out;
> +	}
> +
> +	/*
> +	 * secureboot is enabled if os-secure-enforcing property exists,
> +	 * else disabled.
> +	 */
> +	enabled = of_property_read_bool(node, "os-secure-enforcing");
> +
> +out:

So here you need:

	of_node_put(node);


> +	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
> +	return enabled;
> +}

cheers