Re: [PATCH v2 2/4] lib: update single-char callers of strtobool

[Kees Cook]

On Fri, Feb 5, 2016 at 2:46 AM, David Laight <David.Laight@xxxxxxxxxx> 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