linux-kernel - Re: goldfish driver: Missing get_user_pages in goldfish_pipe_read

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Message-ID: <20130627174651.GA19874@kroah.com>
Date:	Thu, 27 Jun 2013 10:46:51 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	David 'Digit' Turner <digit@...roid.com>,
	Xiaohui Xin <xiaohui.xin@...el.com>,
	Yunhong Jiang <yunhong.jiang@...el.com>,
	Jun Nakajima <jun.nakajima@...el.com>,
	Tom Keel <thomas.keel@...el.com>,
	Alan Cox <alan@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: goldfish driver: Missing get_user_pages in
 goldfish_pipe_read_write()

On Thu, Jun 27, 2013 at 01:35:32PM -0400, Mathieu Desnoyers wrote:
> The following code snippet:
> 
> drivers/platform/goldfish/goldfish_pipe.c:
> goldfish_pipe_read_write()
> 
>                 /* Ensure that the corresponding page is properly mapped */
>                 /* FIXME: this isn't safe or sufficient - use get_user_pages */
>                 if (is_write) {
>                         char c;
>                         /* Ensure that the page is mapped and readable */
>                         if (__get_user(c, (char __user *)address)) {
>                                 if (!ret)
>                                         ret = -EFAULT;
>                                 break;
>                         }
>                 } else {
>                         /* Ensure that the page is mapped and writable */
>                         if (__put_user(0, (char __user *)address)) {
>                                 if (!ret)
>                                         ret = -EFAULT;
>                                 break;
>                         }
>                 }
> 
> Seems to lack the kind of validation required to make it fail properly
> if the memory range is not fully populated.

This is an emulated platform only, so it's probably not a big deal,
right?

> I see that this feature has been merged in Linux kernel 3.9, but the
> FIXME is still there in 3.10-rc7. Any plans on fixing this ?

It would be good to get fixed, but probably way down on the priority
list.

thanks,

greg k-h
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