linux-kernel - Re: [PATCH] platform/x86: wmi: Do not mix pages and kmalloc

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Message-ID: <CAGXu5jL4V9sL7Ai1SVTNkg8OE70c6kLJBdqNtj9Z06MOb4zG0g@mail.gmail.com>
Date:   Wed, 20 Jun 2018 16:43:14 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Darren Hart <dvhart@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Mihai Donțu <mihai.dontu@...il.com>,
        Mario.Limonciello@...l.com
Subject: Re: [PATCH] platform/x86: wmi: Do not mix pages and kmalloc

On Wed, Jun 20, 2018 at 4:37 PM, Darren Hart <dvhart@...radead.org> wrote:
> On Wed, Jun 20, 2018 at 02:31:41PM -0700, Kees Cook wrote:
>> The probe handler_data was being allocated with __get_free_pages()
>> for no reason I could find. The error path was using kfree(). Since
>
> v4 of Mario's series used kmalloc:
> https://patchwork.kernel.org/patch/9985827/
>
> This was changed in v10 to use __get_free_pages:
> https://patchwork.kernel.org/patch/10018023/
>
> But... I'm not finding the discussion that led to this change.... Mario,
> do you recall? Something about contiguous memory? We had a similar
> discussion on an earlier series:
>
> https://patchwork.kernel.org/patch/9975277/

FWIW, kmalloc gets you contiguous memory...

But if the reason is found and needs to stay, the probe error path's
kfree() needs to be fixed, and __GFP_COMP needs to be added to the
free page flags.

-Kees

-- 
Kees Cook
Pixel Security