linux-kernel - Re: [PATCH v1 3/7] powercap/dtpm: Fixup kfree for virtual node

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <2d78266d-0b49-593e-79d8-00215c14fde5@linaro.org>
Date:   Tue, 22 Feb 2022 16:59:29 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     rjw@...ysocki.net, heiko@...ech.de, lukasz.luba@....com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Daniel Lezcano <daniel.lezcano@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v1 3/7] powercap/dtpm: Fixup kfree for virtual node

On 22/02/2022 16:55, Ulf Hansson wrote:
> On Fri, 18 Feb 2022 at 14:18, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>>
>> On 17/02/2022 16:45, Ulf Hansson wrote:
>>
>> [ ... ]
>>
>>> Does ops->release() also resets the "dtpm" pointer to NULL? If not,
>>> it's good practice that it should, right?
>>>
>>> In that case, we would be calling "kfree(NULL);" the second time,
>>> which is perfectly fine.
>>
>> So you suggest to replace:
>>
>> if (ops->release)
>>          ops->release(dtpm);
>> else
>>          kfree(dtpm);
>>
>> By:
>>
>> if (ops->release) {
>>          ops->release(dtpm);
>>          dtpm = NULL;
>> }
>>
> 
> I don't have a strong opinion how to code this.
> 
> What I was trying to point out was that if ->ops->release() frees the
> memory it could/should also reset the pointer to NULL

No it can't because it is not a pointer, it is contained by the backend 
specific structure.

eg.

struct dtpm_cpu {
	struct dtpm dtpm;
};

the release frees a dtpm_cpu structure.



> And if that is already done, the kfree below is harmless and there
> would be nothing to "fix".
> 
>> kfree(dtpm);
>>
>> ?
> 
> Kind regards
> Uffe


-- 
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog