linux-kernel - Re: [PATCH 11/12] IMA: turn ima_policy_flags into __wr_after

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Date:   Thu, 20 Dec 2018 15:30:01 -0200
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Igor Stoppa <igor.stoppa@...il.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>, igor.stoppa@...wei.com,
        Nadav Amit <nadav.amit@...il.com>,
        Kees Cook <keescook@...omium.org>,
        linux-integrity@...r.kernel.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/12] IMA: turn ima_policy_flags into __wr_after_init


Hello Igor,

Igor Stoppa <igor.stoppa@...il.com> writes:

> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 59d834219cd6..5f4e13e671bf 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -21,6 +21,7 @@
>  #include <linux/scatterlist.h>
>  #include <linux/slab.h>
>  #include <linux/err.h>
> +#include <linux/prmem.h>
>
>  #include "ima.h"
>
> @@ -98,9 +99,9 @@ void __init ima_load_x509(void)
>  {
>  	int unset_flags = ima_policy_flag & IMA_APPRAISE;
>
> -	ima_policy_flag &= ~unset_flags;
> +	wr_assign(ima_policy_flag, ima_policy_flag & ~unset_flags);
>  	integrity_load_x509(INTEGRITY_KEYRING_IMA, CONFIG_IMA_X509_PATH);
> -	ima_policy_flag |= unset_flags;
> +	wr_assign(ima_policy_flag, ima_policy_flag | unset_flags);
>  }
>  #endif

In the cover letter, you said:

> As the name implies, the write protection kicks in only after init()
> is completed; before that moment, the data is modifiable in the usual
> way.

Given that, is it still necessary or useful to use wr_assign() in a
function marked with __init?

--
Thiago Jung Bauermann
IBM Linux Technology Center