linux-kernel - Re: [PATCH] asm-generic: Force cast get

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Date:   Fri, 24 Feb 2017 17:24:52 -0800
From:   Stephen Boyd <stephen.boyd@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Subject: Re: [PATCH] asm-generic: Force cast get_user() setting x to 0

Quoting Stephen Boyd (2017-02-17 08:52:29)
> If we call get_user() with an __le* or __be* type sparse will
> complain when we assign the result to 0 on the faulting path.
> Let's force cast here so that sparse doesn't complain. This
> mirrors what we do in __get_user() as well.
> 
> Signed-off-by: Stephen Boyd <stephen.boyd@...aro.org>
> ---
> 
> I made a similar fix to arm64 headers, and it looks like asm-generic
> would need the same fix.

I suppose we can ignore this. I was using sparse v0.5.0 but it seems
that later versions of sparse don't complain here anymore as Luc has
pointed out.

-Stephen

> 
>  include/asm-generic/uaccess.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
> index cc6bb319e464..6352d61df7eb 100644
> --- a/include/asm-generic/uaccess.h
> +++ b/include/asm-generic/uaccess.h
> @@ -227,7 +227,7 @@ extern int __put_user_bad(void) __attribute__((noreturn));
>         might_fault();                                          \
>         access_ok(VERIFY_READ, __p, sizeof(*ptr)) ?             \
>                 __get_user((x), (__typeof__(*(ptr)) *)__p) :    \
> -               ((x) = (__typeof__(*(ptr)))0,-EFAULT);          \
> +               ((x) = (__force __typeof__(*(ptr)))0, -EFAULT); \
>  })
>  
>  #ifndef __get_user_fn