linux-kernel - Re: [PATCH 2/3 RESEND] ptrace: cleanup address space conversion on ptrace

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Date:	Mon, 23 Aug 2010 12:21:05 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>, Roland McGrath <roland@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3 RESEND] ptrace: cleanup address space conversion on
 ptrace_request()

On Tue, Aug 24, 2010 at 01:06:15AM +0900, Namhyung Kim wrote:
> In some cases 'data' should be considered as a user pointer but it requires
> cast with additional __force markup which was missing. Rather than add the
> markups wherever needed, make use of a temporary variable of user pointer.
> This patch is based on compat_ptrace_request() implementation.
> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Namhyung Kim <namhyung@...il.com>
> ---
>  kernel/ptrace.c |   13 +++++++------
>  1 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 4afd9b8..7547b1c 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -564,6 +564,7 @@ int ptrace_request(struct task_struct *child, long request,
>  {
>  	int ret = -EIO;
>  	siginfo_t siginfo;
> +	unsigned long __user *datap = (unsigned long __user __force *) data;

Just make this a

	void __user *datap = (void __user *)data;

and you can pass it around withjout additional casts.  Also no need
for the force here I think.

You'll still need a cast for the put_user calls, or you could just
convert them to copy_to_user which is fine with a void pointer.
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