linux-kernel - Re: [PATCH v2] kbuild: treat char as always unsigned

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Message-ID: <CAHmME9ox7JNqOOZHEHCgaS95rsn-dVr4QOnN1mfmFEn=i9_jvw@mail.gmail.com>
Date:   Mon, 24 Oct 2022 19:17:25 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-toolchains@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kalle Valo <kvalo@...nel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Larry Finger <Larry.Finger@...inger.net>, mikem@...g3k.org,
        wlanfae@...ltek.com
Subject: Re: [PATCH v2] kbuild: treat char as always unsigned

Hi Linus,

On Mon, Oct 24, 2022 at 7:11 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> IOW, I don't think these are 6.1 material as some kind of obvious
> fixes, at least not without driver author acks.

Right, these are posted to the authors and maintainers to look at.
Maybe they punt them until 6.2 which would be fine too.

> On Mon, Oct 24, 2022 at 9:34 AM Jason A. Donenfeld <Jason@...c4.com> wrote:
> Some of those may need more thought. For example, that first one:
>
> > https://lore.kernel.org/all/20221024163005.536097-1-Jason@zx2c4.com
>
> looks just *strange*. As far as I can tell, no other wireless drivers
> do any sign checks at all.
>
> Now, I didn't really look around a lot, but looking at a few other
> SIOCSIWESSID users, most don't even seem to treat it as a string at
> all, but as just a byte dump (so memcpy() instead of strncpy())
>
> As far as I know, there are no actual rules for SSID character sets,
> and while using utf-8 or something else might cause interoperability
> problems, this driver seems to be just confused. If you want to check
> for "printable characters", that check is still wrong.
>
> So I don't think this is a "assume char is signed" issue. I think this
> is a "driver is confused" issue.

Yea I had a few versions of this. In one of them, I changed `char
*extra` throughout the wireless stack into `s8 *extra` and in another
`u8 *extra`, after realizing they're mostly just bags of bits. But
that seemed pretty invasive when, indeed, this staging driver is just
a little screwy.

So perhaps the right fix is to just kill that whole snippet? Kalle - opinions?

Jason