linux-kernel - Re: [PATCH] Use kzfree in tty buffer management to enforce data sanitization

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Date:	Sun, 31 May 2009 09:24:22 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Larry H." <research@...reption.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Rik van Riel <riel@...hat.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] Use kzfree in tty buffer management to enforce data 
	sanitization

Hi Linus,

On Sat, 30 May 2009, Larry H. wrote:
>>
>> This patch doesn't affect fastpaths.

On Sun, May 31, 2009 at 5:04 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> This patch is ugly as hell.
>
> You already know the size of the data to clear.
>
> If we actually wanted this (and I am in _no_way_ saying we do), the only
> sane thing to do is to just do
>
>        memset(buf->data, 0, N_TTY_BUF_SIZE);
>        if (PAGE_SIZE != N_TTY_BUF_SIZE)
>                kfree(...)
>        else
>                free_page(...)
>
>
> but quite frankly, I'm not convinced about these patches at all.

I wonder why the tty code has that N_TTY_BUF_SIZE special casing in
the first place? I think we can probably just get rid of it and thus
we can use kzfree() here if we want to.

                                 Pekka
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