From: Kees Cook <keescook@chromium.org>
To: David Laight <David.Laight@aculab.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Amitkumar Karwar <akarwar@marvell.com>,
Nishant Sarmukadam <nishants@marvell.com>,
Kalle Valo <kvalo@codeaurora.org>,
Steve French <sfrench@samba.org>,
"linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
Joe Perches <joe@perches.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Daniel Borkmann <daniel@iogearbox.net>,
Michael Ellerman <mpe@ellerman.id.au>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
"x86@kernel.org" <x86@kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/4] lib: update single-char callers of strtobool
Date: Fri, 5 Feb 2016 13:18:04 -0800 [thread overview]
Message-ID: <CAGXu5jJrFv5Y8Q_i3yFYBDmT0+pO05dS3ijB0gOn-huasxZWmA@mail.gmail.com> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1CCD6FE5@AcuExch.aculab.com>
On Fri, Feb 5, 2016 at 2:46 AM, David Laight <David.Laight@aculab.com> wrote:
> From: Kees Cook
>> Sent: 04 February 2016 21:01
>> Some callers of strtobool were passing a pointer to unterminated strings.
>> In preparation of adding multi-character processing to kstrtobool, update
>> the callers to not pass single-character pointers, and switch to using the
>> new kstrtobool_from_user helper where possible.
>
> Personally I think you should change the name of the function so that the
> compiler (and linker) will pick up places that have not been changed.
> Relying on people to make the required changes will cause problems.
After the single-character users were pointed out, I looked for others
and there aren't any.
> The current code (presumably) treats "no", "nyet" and "nkjkkrkjrkjterkj" as false.
> Changing that behaviour will break things.
There's no change there. All three of those will still be "false".
Perhaps my changelog shouldn't say "unterminated" but rather
"character array".
> If you want to support "on" and "off", then maybe check for the supplied string
> starting with the character sequences "on\0" and "off\0" (as well as any others).
> This doesn't need the input string be '\0' terminated - since you match y and n
> without looking at the 2nd byte.
> You'd have to be extremely unlucky to get a page fault in the 3 bytes
> following an 'o' if the caller supplied a single byte buffer.
I'd prefer to keep the switch statement as short as possible, and I
don't want to do full string compares. And as you say, even fixing the
single-byte callers seems like a needless exercise, but seeing as how
it's a net clean-up, I think it's good they way I've got the series.
-Kees
--
Kees Cook
Chrome OS & Brillo Security
next prev parent reply other threads:[~2016-02-05 21:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-04 21:00 [PATCH v2 0/4] lib: add "on" and "off" to strtobool Kees Cook
2016-02-04 21:00 ` [PATCH v2 1/4] lib: move strtobool to kstrtobool Kees Cook
2016-02-04 22:43 ` Andy Shevchenko
2016-02-04 22:48 ` Kees Cook
2016-02-04 23:55 ` Rasmus Villemoes
2016-02-05 20:50 ` Kees Cook
2016-02-04 21:00 ` [PATCH v2 2/4] lib: update single-char callers of strtobool Kees Cook
2016-02-04 22:59 ` Andy Shevchenko
2016-02-04 23:01 ` Kees Cook
2016-02-05 10:46 ` David Laight
2016-02-05 21:18 ` Kees Cook [this message]
2016-02-04 21:00 ` [PATCH v2 3/4] lib: add "on"/"off" support to kstrtobool Kees Cook
2016-02-04 23:00 ` Andy Shevchenko
2016-02-04 23:11 ` Kees Cook
2016-02-04 21:00 ` [PATCH v2 4/4] param: convert some "on"/"off" users to strtobool Kees Cook
2016-02-04 23:04 ` Andy Shevchenko
2016-02-05 0:11 ` Kees Cook
2016-02-05 2:12 ` Kees Cook
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