linux-kernel - Re: [PATCH] lib/usercopy: fix sparse errors

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Date:   Sun, 17 Dec 2017 18:21:40 +0100
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/usercopy: fix sparse errors

On Sat, Dec 09, 2017 at 05:24:24PM +0100, Christophe Leroy wrote:
>   CHECK   lib/usercopy.c
> lib/usercopy.c:26:13: warning: incorrect type in argument 1 (different address spaces)
> lib/usercopy.c:26:13:    expected void const volatile [noderef] <asn:1>*<noident>
> lib/usercopy.c:26:13:    got void *to
> lib/usercopy.c:27:34: warning: incorrect type in argument 1 (different address spaces)
> lib/usercopy.c:27:34:    expected void const volatile *p
> lib/usercopy.c:27:34:    got void const [noderef] <asn:1>*from
> lib/usercopy.c:28:38: warning: incorrect type in argument 1 (different address spaces)
> lib/usercopy.c:28:38:    expected void [noderef] <asn:1>*to
> lib/usercopy.c:28:38:    got void *to
> lib/usercopy.c:28:42: warning: incorrect type in argument 2 (different address spaces)
> lib/usercopy.c:28:42:    expected void const *from
> lib/usercopy.c:28:42:    got void const [noderef] <asn:1>*from
> lib/usercopy.c:23:15: error: symbol '_copy_to_user' redeclared with different type (originally declared at ./include/linux/uaccess.h:140) - incompatible argument 1 (different address spaces)
>   CC      lib/usercopy.o
> 
> Fixes: d597580d37377 ("generic ...copy_..._user primitives")
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>  lib/usercopy.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/usercopy.c b/lib/usercopy.c
> index 15e2e6f..3744b2a 100644
> --- a/lib/usercopy.c
> +++ b/lib/usercopy.c
> @@ -20,7 +20,7 @@ EXPORT_SYMBOL(_copy_from_user);
>  #endif
>  
>  #ifndef INLINE_COPY_TO_USER
> -unsigned long _copy_to_user(void *to, const void __user *from, unsigned long n)
> +unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
>  {
>  	might_fault();
>  	if (likely(access_ok(VERIFY_WRITE, to, n))) {
> -- 

Hi,

The change is good.
The commit message would better simply describe the problem instead
of describing the symptom. For example, something like:
	The function _copy_to_user() is used to copy to address space.
	As such, the destination pointer should be annotated with
	'__user'.
	However, the function has the annotation wrongly, on the
	source instead of the destination (copy & paste error?).
	Fix this by moving the __user annotation to the correct
	argument.


-- Luc Van Oostenryck