linux-kernel - Re: [GIT PULL] percpu fix for v5.9-rc6

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Date:   Fri, 18 Sep 2020 13:14:54 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [GIT PULL] percpu fix for v5.9-rc6

On Fri, Sep 18, 2020 at 1:02 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> I suppose it's not really necessary, we could do offsetof here, right?

Yup, that would make a lot more sense.

But right now, the sizeof() obviously silently works.

As do a number of other fairly nonsensical things, like assigning a struct etc.

And yes, I realize we may well do that too. But I think that's a
dangerous pattern too, ie doing

   *a = *b;

silently works, and copies everything but the final array.

And yes - none of this is _worse_ than using zero-sized arrays, but
the point is that it isn't better either.

            Linus