linux-hardening - Re: [PATCH RESEND][next] rtl8xxxu: Fix fall-through warnings for Clang

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Date:   Wed, 10 Mar 2021 14:51:24 -0500
From:   Jes Sorensen <jes.sorensen@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH RESEND][next] rtl8xxxu: Fix fall-through warnings for
 Clang

On 3/10/21 2:45 PM, Kees Cook wrote:
> On Wed, Mar 10, 2021 at 02:31:57PM -0500, Jes Sorensen wrote:
>> On 3/10/21 2:14 PM, Kees Cook wrote:
>>> Hm, this conversation looks like a miscommunication, mainly? I see
>>> Gustavo, as requested by many others[1], replacing the fallthrough
>>> comments with the "fallthrough" statement. (This is more than just a
>>> "Clang doesn't parse comments" issue.)
>>>
>>> This could be a tree-wide patch and not bother you, but Greg KH has
>>> generally advised us to send these changes broken out. Anyway, this
>>> change still needs to land, so what would be the preferred path? I think
>>> Gustavo could just carry it for Linus to merge without bothering you if
>>> that'd be preferred?
>>
>> I'll respond with the same I did last time, fallthrough is not C and
>> it's ugly.
> 
> I understand your point of view, but this is not the consensus[1] of
> the community. "fallthrough" is a macro, using the GCC fallthrough
> attribute, with the expectation that we can move to the C17/C18
> "[[fallthrough]]" statement once it is finalized by the C standards
> body.

I don't know who decided on that, but I still disagree. It's an ugly and
pointless change that serves little purpose. We shouldn't have allowed
the ugly /* fall-through */ comments in either, but at least they didn't
mess with the code. I guess when you give someone an inch, they take a mile.

Last time this came up, the discussion was that clang refused to fix
their brokenness and therefore this nonsense was being pushed into the
kernel. It's still a pointless argument, if clang can't fix it's crap,
then stop using it.

As Kalle correctly pointed out, none of the previous comments to this
were addressed, the patches were just reposted as fact. Not exactly a
nice way to go about it either.

Jes