linux-kernel - Re: [PATCH 1/7] pipe, sysctl: drop 'min' parameter from pipe-max-size converter

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Message-ID: <CAGXu5jJt+gv=CKv_2Dekf2RxiY_=sdz8OCpxzouP3CFNeGT6+Q@mail.gmail.com>
Date:   Wed, 10 Jan 2018 09:30:13 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Willy Tarreau <w@....eu>,
        Mikulas Patocka <mpatocka@...hat.com>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH 1/7] pipe, sysctl: drop 'min' parameter from pipe-max-size converter

On Tue, Jan 9, 2018 at 6:29 PM, Eric Biggers <ebiggers3@...il.com> wrote:
> On Tue, Jan 09, 2018 at 02:20:45PM -0800, Kees Cook wrote:
>> On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers <ebiggers3@...il.com> wrote:
>> > From: Eric Biggers <ebiggers@...gle.com>
>> >
>> > Before validating the given value against pipe_min_size,
>> > do_proc_dopipe_max_size_conv() calls round_pipe_size(), which rounds the
>> > value up to pipe_min_size.  Therefore, the second check against
>> > pipe_min_size is redundant.  Remove it.
>>
>> Well, it's not redundant: it provides a hint to anyone trying to tweak
>> the sysctl about the minimum value. I think this should stay, but that
>> pipe_min_size should be made const.
>>
>> -Kees
>>
>
> It *is* redundant, because it doesn't do anything.  round_pipe_size() already
> rounds the value up to the minimum.

Ah, yes, I see it now. Wow are the sysctl functions convoluted here!

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook
Pixel Security