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References: <20220519125505.92400-1-songmuchun@bytedance.com> <YoZBbcEHcLqsAssF@casper.infradead.org>
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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Thu, 19 May 2022 22:10:54 +0800
Message-ID: <CAMZfGtWw0Jm0fr=m38djPtCpTkVPvqku5vjCmOmGgDtOHZn9Aw@mail.gmail.com>
Subject: Re: [PATCH] sysctl: handle table->maxlen properly for proc_dobool
To:     Matthew Wilcox <willy@infradead.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        Muchun Song <smuchun@gmail.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>
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On Thu, May 19, 2022 at 9:09 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Thu, May 19, 2022 at 08:55:05PM +0800, Muchun Song wrote:
> > @@ -428,6 +428,8 @@ static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
> >                               int write, void *data)
> >  {
> >       if (write) {
> > +             if (*negp || (*lvalp != 0 && *lvalp != 1))
> > +                     return -EINVAL;
> >               *(bool *)valp = *lvalp;
> >       } else {
> >               int val = *(bool *)valp;
>
> Is this the right approach?  Or should we do as C does and interpret
> writing non-zero as true?  ie:

All right. We could obey the C rule here.

>
>                 *(bool *)valp = (bool)*lvalp;
>
> (is that cast needed?  It wouldn't be if it were an int, but bool is a
> bit weird)
>

If the cast is weird. How about:

        *(bool *)valp = *lvalp ? true : false;

Thanks.