linux-kernel - goldfish driver: Missing get_user_pages in goldfish_pipe_read

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Message-ID: <20130627173532.GA29405@Krystal>
Date:	Thu, 27 Jun 2013 13:35:32 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: goldfish driver: Missing get_user_pages in
	goldfish_pipe_read_write()

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.

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 ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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