linux-kernel - Re: [PATCH v10 1/6] IMA: Check IMA policy flag

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Date:   Tue, 10 Dec 2019 17:42:29 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        linux-integrity@...r.kernel.org
Cc:     eric.snowberg@...cle.com, dhowells@...hat.com,
        mathew.j.martineau@...ux.intel.com, matthewgarrett@...gle.com,
        sashal@...nel.org, jamorris@...ux.microsoft.com,
        linux-kernel@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH v10 1/6] IMA: Check IMA policy flag

On Wed, 2019-12-04 at 14:41 -0800, Lakshmi Ramasubramanian wrote:
> Return immediately from process_buffer_measurement()
> if the IMA policy flag is set to zero. Not doing this
> can result in kernel panic when process_buffer_measurement()
> is called before IMA is initialized (for instance, when
> the IMA hook is called when a key is added to
> the .builtin_trusted_keys keyring).
> 
> This change adds the check in process_buffer_measurement()
> to return immediately if ima_policy_flag is set to zero.

Patch descriptions aren't suppose to be written as pseudo code.  Start
with the current status and problem description.

For example, "process_buffer_measurement() may be called prior to IMA being initialized, which would result in a kernel panic.  This patch ..."

Mimi

> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  security/integrity/ima/ima_main.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index d7e987baf127..9b35db2fc777 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -655,6 +655,9 @@ void process_buffer_measurement(const void *buf, int size,
>  	int action = 0;
>  	u32 secid;
>  
> +	if (!ima_policy_flag)
> +		return;
> +
>  	/*
>  	 * Both LSM hooks and auxilary based buffer measurements are
>  	 * based on policy.  To avoid code duplication, differentiate