linux-kernel - [PATCH 0/2] base/platform: Platform data and resources NULL handling

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Message-ID: <20100907133107.GA21463@oksana.dev.rtsoft.ru>
Date:	Tue, 7 Sep 2010 17:31:07 +0400
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] base/platform: Platform data and resources NULL
 handling

Hi all,

There is a bug in the MFD core code (drivers/mfd/mfd-core.c),
the mfd_add_device function does not check platform_data for NULL,
and thus always calls platform_device_add_data():

static int mfd_add_device(struct device *parent, int id, [...])
{
	[...]
	ret = platform_device_add_data(pdev,
		cell->platform_data, cell->data_size);
	[...]
}

The problem is that when cell->platform_data is NULL, the platform
core calls kmemdup(NULL, 0, ...), which returns a non-NULL result
(ZERO_SIZE_PTR), and the result is stored in the dev.platform_data.
This causes drivers to oops on a valid code:

if (pdata)
	stuff = pdata->stuff;

Firstly I thought that I would fix the MFD core, but it appears
that the better approach would be to change device_add_data() call
behaviour, and thus make the core code more safe.

There are two patches: a patch that is necessary for the bug fix,
and a non-essential cleanup patch.

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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