linux-kernel - Re: [PATCH] fs, binfmt_aout: Fix pointer warnings

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Message-Id: <20100309.101121.193684481.d.hatayama@jp.fujitsu.com>
Date:	Tue, 09 Mar 2010 10:11:21 +0900 (JST)
From:	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>
To:	petkovbb@...glemail.com
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs, binfmt_aout: Fix pointer warnings

Thanks for your report.

From: Borislav Petkov <petkovbb@...glemail.com>
Subject: [PATCH] fs, binfmt_aout: Fix pointer warnings
Date: Mon, 8 Mar 2010 16:46:01 +0100

> Hi,
> 
> I'm getting the warnings in the commit message below with current git. Maybe fix
> them like this:
> 
> --
> From: Borislav Petkov <petkovbb@...il.com>
> Date: Mon, 8 Mar 2010 16:37:42 +0100
> Subject: [PATCH] fs, binfmt_aout: Fix pointer warnings
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
> I get
> 
> fs/binfmt_aout.c: In function ‘aout_core_dump’:
> fs/binfmt_aout.c:125: warning: passing argument 2 of ‘dump_write’ makes pointer from integer without a cast
> include/linux/coredump.h:12: note: expected ‘const void *’ but argument is of type ‘long unsigned int’
> fs/binfmt_aout.c:132: warning: passing argument 2 of ‘dump_write’ makes pointer from integer without a cast
> include/linux/coredump.h:12: note: expected ‘const void *’ but argument is of type ‘long unsigned int’
> 
> due to dump_write() expecting a user void *. Fold casts into the
> START_DATA/START_STACK macros and shut up the warnings.
> 
> Signed-off-by: Borislav Petkov <petkovbb@...il.com>
> ---
>  fs/binfmt_aout.c |   14 ++++++++------
>  1 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
> index 15d80bb..9b6aef0 100644
> --- a/fs/binfmt_aout.c
> +++ b/fs/binfmt_aout.c
> @@ -75,14 +75,16 @@ static int aout_core_dump(struct coredump_params *cprm)
>  	struct file *file = cprm->file;
>  	mm_segment_t fs;
>  	int has_dumped = 0;
> -	unsigned long dump_start, dump_size;
> +	void __user *dump_start;
> +	int dump_size;
>  	struct user dump;
>  #ifdef __alpha__
> -#       define START_DATA(u)	(u.start_data)
> +#       define START_DATA(u)	((void __user *)u.start_data)
>  #else
> -#	define START_DATA(u)	((u.u_tsize << PAGE_SHIFT) + u.start_code)
> +#	define START_DATA(u)	((void __user *)((u.u_tsize << PAGE_SHIFT) + \
> +				 u.start_code))
>  #endif
> -#       define START_STACK(u)   (u.start_stack)
> +#       define START_STACK(u)   ((void __user *)u.start_stack)
>  
>  	fs = get_fs();
>  	set_fs(KERNEL_DS);
> @@ -104,9 +106,9 @@ static int aout_core_dump(struct coredump_params *cprm)
>  
>  /* make sure we actually have a data and stack area to dump */
>  	set_fs(USER_DS);
> -	if (!access_ok(VERIFY_READ, (void __user *)START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
> +	if (!access_ok(VERIFY_READ, START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
>  		dump.u_dsize = 0;
> -	if (!access_ok(VERIFY_READ, (void __user *)START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
> +	if (!access_ok(VERIFY_READ, START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
>  		dump.u_ssize = 0;

Your fixing looks reasonable to me. I understand your patch set as
follows.

 - The START_DATA() and START_STACK() macro calls are all passed to
   the arguments of type (void *), meaning that they need casts in
   the appropreate positions.

 - Moreover, they are more natural to be used directly as (void *)
   than to be casted outside the macro.

Thanks.

>  
>  	set_fs(KERNEL_DS);
> -- 
> 1.6.6.1
>