linux-kernel - Re: [PATCH v2 1/7] gpio: mockup: improve the debugfs input sanitization

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Message-ID: <CAMRc=MeEFLyLzEeAy552mk+-CSSR6e_cu0kmpQEqEOF2_7zkSA@mail.gmail.com>
Date:   Wed, 31 May 2017 12:52:13 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/7] gpio: mockup: improve the debugfs input sanitization

2017-05-30 20:52 GMT+02:00 Andy Shevchenko <andy.shevchenko@...il.com>:
> On Tue, May 30, 2017 at 11:58 AM, Bartosz Golaszewski <brgl@...ev.pl> wrote:
>> We're currently only checking the first character of the input to the
>> debugfs event files, so a string like '0sdfdsf' is valid and indicates
>> a falling edge event.
>>
>> Be more strict and only allow '0', '1', '0\n' & '1\n'.
>>
>> While we're at it: move the sanitization code before the irq_enabled
>> check so that we indicate an error on invalid input even if nobody is
>> waiting for events.
>
>> -       int val;
>> -       char buf;
>> +       int rv, val;
>
>> +       rv = kstrtoint_from_user(usr_buf, size, 0, &val);
>> +       if (rv)
>> +               return rv;
>
>> +       if (val != 0 && val != 1)
>
> Wouldn't be easier to have
>
> u8 rv;
>
> ret = kstrtu8_from_user();
> if (ret >= 2)
>  return ...;
>
> ?

kstrtu8_from_user() doesn't return the converted value, so you won't
skip an if anyway and by using the int variant, we're avoiding a cast.
I'd prefer it this way frankly.

Thanks,
Bartosz