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

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Message-ID: <bb8cb502-d958-c4b4-eb82-603799079b63@gmail.com>
Date:   Thu, 20 Dec 2018 19:49:52 +0200
From:   Igor Stoppa <igor.stoppa@...il.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.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

Hi,

On 20/12/2018 19:30, Thiago Jung Bauermann wrote:
> 
> 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?

I might have been over enthusiastic of using the wr interface.
You are right, I can drop these two. Thank you.

--
igor