linux-kernel - Re: [RESEND PATCH v2 10/16] clk: move checking .git_parent to __clk_core

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

Date:	Tue, 2 Feb 2016 11:19:51 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-clk@...r.kernel.org,
	Michael Turquette <mturquette@...libre.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v2 10/16] clk: move checking .git_parent to __clk_core_init()

Hi Stephen,



2016-02-02 9:50 GMT+09:00 Stephen Boyd <sboyd@...eaurora.org>:
> On 12/28, Masahiro Yamada wrote:
>> The .git_parent is mandatory for multi-parent clocks.  Move the check
>
> s/git/get/
>
> Same for the subject.
>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index e6e10f5..4ad0a36 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -1677,13 +1677,6 @@ static struct clk_core *__clk_init_parent(struct clk_core *core)
>>               goto out;
>>       }
>>
>> -     if (!core->ops->get_parent) {
>> -             WARN(!core->ops->get_parent,
>> -                     "%s: multi-parent clocks must implement .get_parent\n",
>> -                     __func__);
>> -             goto out;
>> -     }
>> -
>>       /*
>>        * Do our best to cache parent clocks in core->parents.  This prevents
>>        * unnecessary and expensive lookups.  We don't set core->parent here;
>> @@ -2315,6 +2308,11 @@ static int __clk_core_init(struct clk_core *core)
>>               goto out;
>>       }
>>
>> +     if (core->num_parents > 1 && !core->ops->get_parent) {
>> +             pr_err("%s: %s must implement .get_parent as it has multi parents\n",
>> +                    __func__, core->name);
>> +     }
>> +
>
> This would seem to allow a case where we may deref a null
> get_parent op if it isn't set and we call __clk_init_parent().
> The next patch removes that case by restructuring
> __clk_init_parent(), so we should just combine these two patches
> together and that theoretical problem goes away.
>

I think the case never happens.

__clk_init_parent() is a static function that is only called from
__clk_core_init().
So, the null pointer for .get_parent() has been already checked before
__clk_init_parent().




-- 
Best Regards
Masahiro Yamada