linux-kernel - Re: [PATCH] ima: Fix sizeof mismatches

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Message-ID: <0ceb198a-a313-f542-49cc-c0b9f6b1ea52@canonical.com>
Date:   Mon, 12 Oct 2020 19:10:19 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Joe Perches <joe@...ches.com>, Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Roberto Sassu <roberto.sassu@...ito.it>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ima: Fix sizeof mismatches

On 12/10/2020 19:06, Joe Perches wrote:
> On Mon, 2020-10-12 at 13:51 -0400, Mimi Zohar wrote:
>> On Wed, 2020-10-07 at 11:27 -0700, Joe Perches wrote:
>>> On Wed, 2020-10-07 at 12:02 +0100, Colin King wrote:
>>>> An incorrect sizeof is being used, sizeof(*fields) is not correct,
>>>> it should be sizeof(**fields). This is not causing a problem since
>>>> the size of these is the same. Fix this in the kmalloc_array and
>>>> memcpy calls.
>>> []
>>>> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
>>> []
>>>> @@ -216,11 +216,11 @@ int template_desc_init_fields(const char *template_fmt,
>>>>  	}
>>>>  
>>>>  	if (fields && num_fields) {
>>>> -		*fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
>>>> +		*fields = kmalloc_array(i, sizeof(**fields), GFP_KERNEL);
>>>>  		if (*fields == NULL)
>>>>  			return -ENOMEM;
>>>>  
>>>> -		memcpy(*fields, found_fields, i * sizeof(*fields));
>>>> +		memcpy(*fields, found_fields, i * sizeof(**fields));
>>>
>>> Maybe use kmemdup instead.
>>>
>>> 	if (fields && num_fields) {
>>> 		*fields = kmemdup(found_fields, i * sizeof(**fields), GFP_KERNEL);
>>> 		etc...
>>>
>>
>> Thanks, Joe.  Since this patch will be backported, perhaps it would be
>> better to leave this as a bug fix and upstream other changes
>> independently.
> 
> IMO:
> 
> This patch doesn't need need backporting as it doesn't
> actually fix anything other than a style defect.
> 
> void * and void ** are the same size.

indeed, same size, it's a semantic difference *and* a style fix :-)

Colin

> 
> cheers, Joe
>