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Date: Mon, 12 Mar 2018 09:46:16 +1100
From: "Tobin C. Harding" <me@tobin.cc>
To: Linus Torvalds <torvalds@linux-foundation.org>
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Subject: Re: [PATCH v3] kernel.h: Skip single-eval logic on literals in
 min()/max()
Message-ID: <20180311224616.GJ16734@eros>
References: <20180309200536.GA5670@beast>
 <CA+55aFy82Drgu2xm1GWaDz2Jyj5QBx3dW4AatXzmCx-b1YET5Q@mail.gmail.com>
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On Fri, Mar 09, 2018 at 01:10:30PM -0800, Linus Torvalds wrote:
> On Fri, Mar 9, 2018 at 12:05 PM, Kees Cook <keescook@chromium.org> wrote:
> > When max() is used in stack array size calculations from literal values
> > (e.g. "char foo[max(sizeof(struct1), sizeof(struct2))]", the compiler
> > thinks this is a dynamic calculation due to the single-eval logic, which
> > is not needed in the literal case. This change removes several accidental
> > stack VLAs from an x86 allmodconfig build:
> 
> Ok, looks good.
> 
> I just have a couple of questions about applying it.
> 
> In particular, if this will help people working on getting rid of
> VLA's in the short term, I can apply it directly. But if people who
> are looking at it (anybody else than Kees?) don't much care, then this
> might be a 4.17 thing or at least "random -mm queue"?

It's easy enough to work on the other VLA removals without basing on
this, no rush.


thanks,
Tobin.