linux-kernel - Re: [PATCH] powerpc/uaccess: fix warning/error with access

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Message-ID: <4d7c00d5-f42f-1eff-c5c5-34903f342d40@c-s.fr>
Date:   Thu, 18 Oct 2018 11:19:36 +0200
From:   Christophe LEROY <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/uaccess: fix warning/error with access_ok()



Le 18/10/2018 à 10:48, Christophe Leroy a écrit :
> With the following peace of code, the following compilation warning
> is encountered:
> 
> 	if (_IOC_DIR(ioc) != _IOC_NONE) {
> 		int verify = _IOC_DIR(ioc) & _IOC_READ ? VERIFY_WRITE : VERIFY_READ;
> 
> 		if (!access_ok(verify, ioarg, _IOC_SIZE(ioc))) {
> 
> drivers/platform/test/dev.c: In function ‘my_ioctl’:
> drivers/platform/test/dev.c:219:7: warning: unused variable ‘verify’ [-Wunused-variable]
>     int verify = _IOC_DIR(ioc) & _IOC_READ ? VERIFY_WRITE : VERIFY_READ;
> 
> This patch fixes it by handing the type to __access_ok(), changing it
> to an inline function for PPC64 as already done for PPC32

Oops, not that easy, there are places using __access_ok() directly, 
those need to be modified as well.

Christophe

> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>   arch/powerpc/include/asm/uaccess.h | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 15bea9a0f260..97faf0353919 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -47,13 +47,16 @@ static inline void set_fs(mm_segment_t fs)
>    * This check is sufficient because there is a large enough
>    * gap between user addresses and the kernel addresses
>    */
> -#define __access_ok(addr, size, segment)	\
> -	(((addr) <= (segment).seg) && ((size) <= (segment).seg))
> +static inline int __access_ok(int type, unsigned long addr, unsigned long size,
> +			      mm_segment_t seg)
> +{
> +	return addr <= seg.seg && size <= seg.seg;
> +}
>   
>   #else
>   
> -static inline int __access_ok(unsigned long addr, unsigned long size,
> -			mm_segment_t seg)
> +static inline int __access_ok(int type, unsigned long addr, unsigned long size,
> +			      mm_segment_t seg)
>   {
>   	if (addr > seg.seg)
>   		return 0;
> @@ -64,7 +67,7 @@ static inline int __access_ok(unsigned long addr, unsigned long size,
>   
>   #define access_ok(type, addr, size)		\
>   	(__chk_user_ptr(addr),			\
> -	 __access_ok((__force unsigned long)(addr), (size), get_fs()))
> +	 __access_ok((type), (__force unsigned long)(addr), (size), get_fs()))
>   
>   /*
>    * These are the main single-value transfer routines.  They automatically
>