linux-kernel - Re: [GIT PULL] usercopy structs for v5.4-rc2

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Message-ID: <20191004190713.hdfv5h3dppwmz6bs@yavin.dot.cyphar.com>
Date:   Sat, 5 Oct 2019 05:07:13 +1000
From:   Aleksa Sarai <cyphar@...har.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] usercopy structs for v5.4-rc2

On 2019-10-04, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> On Fri, Oct 4, 2019 at 3:42 AM Christian Brauner
> <christian.brauner@...ntu.com> wrote:
> >
> >            The only separate fix we we had to apply
> > was for a warning by clang when building the tests for using the result of
> > an assignment as a condition without parantheses.
> 
> Hmm. That code is ugly, both before and after the fix.
> 
> This just doesn't make sense for so many reasons:
> 
>         if ((ret |= test(umem_src == NULL, "kmalloc failed")))
> 
> where the insanity comes from
> 
>  - why "|=" when you know that "ret" was zero before (and it had to
> be, for the test to make sense)
> 
>  - why do this as a single line anyway?
> 
>  - don't do the stupid "double parenthesis" to hide a warning. Make it
> use an actual comparison if you add a layer of parentheses.

You're quite right -- I was mindlessly copying the "ret |=" logic the
rest of test_user_copy.c does without thinking about it. I'll include a
cleanup for it in the openat2(2) series.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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