Re: [PATCH v2 1/2] serial: samsung: Fix ERR pointer dereference on deferred probe

From: Kevin Hilman <khilman@baylibre.com>
To: Javier Martinez Canillas <javier@osg.samsung.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>,
	linux-serial <linux-serial@vger.kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	linux-samsung-soc@vger.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Sylwester Nawrocki <s.nawrocki@samsung.com>,
	stable@vger.kernel.org
Subject: Re: [PATCH v2 1/2] serial: samsung: Fix ERR pointer dereference on deferred probe
Date: Wed, 1 Jun 2016 14:27:08 -0700	[thread overview]
Message-ID: <CAOi56cWFkdHRufaJEgYq6+ERUZXEdteeJX3+5RzVPCKmBSWFcg@mail.gmail.com> (raw)
In-Reply-To: <46dcde4f-2be6-d633-ad0b-23aa8f684ff6@osg.samsung.com>

Hi Krzysztof,

On Wed, Jun 1, 2016 at 1:57 PM, Javier Martinez Canillas
<javier@osg.samsung.com> wrote:
> Hello Krzysztof,
>
> On 05/31/2016 10:00 AM, Krzysztof Kozlowski wrote:
>> When the clk_get() of "uart" clock returns EPROBE_DEFER, the next re-probe
>> finishes with success but uses invalid (ERR_PTR) values.  This leads to
>> dereferencing of ERR_PTR stored under ourport->clk:
>>
>>       12c30000.serial: Controller clock not found
>>       (...)
>>       12c30000.serial: ttySAC3 at MMIO 0x12c30000 (irq = 61, base_baud = 0) is a S3C6400/10
>>       Unable to handle kernel paging request at virtual address fffffdfb
>>
>>       (clk_prepare) from [<c039f7d0>] (s3c24xx_serial_pm+0x20/0x128)
>>       (s3c24xx_serial_pm) from [<c0395414>] (uart_change_pm+0x38/0x40)
>>       (uart_change_pm) from [<c039689c>] (uart_add_one_port+0x31c/0x44c)
>>       (uart_add_one_port) from [<c03a035c>] (s3c24xx_serial_probe+0x2a8/0x418)
>>       (s3c24xx_serial_probe) from [<c03ee110>] (platform_drv_probe+0x50/0xb0)
>>       (platform_drv_probe) from [<c03ecb44>] (driver_probe_device+0x1f4/0x2b0)
>>       (driver_probe_device) from [<c03eb0c0>] (bus_for_each_drv+0x44/0x8c)
>>       (bus_for_each_drv) from [<c03ec8c8>] (__device_attach+0x9c/0x100)
>>       (__device_attach) from [<c03ebf54>] (bus_probe_device+0x84/0x8c)
>>       (bus_probe_device) from [<c03ec388>] (deferred_probe_work_func+0x60/0x8c)
>>       (deferred_probe_work_func) from [<c012fee4>] (process_one_work+0x120/0x328)
>>       (process_one_work) from [<c0130150>] (worker_thread+0x2c/0x4ac)
>>       (worker_thread) from [<c0135320>] (kthread+0xd8/0xf4)
>>       (kthread) from [<c0107978>] (ret_from_fork+0x14/0x3c)
>>
>> The first unsuccessful clk_get() causes s3c24xx_serial_init_port() to
>> exit with failure but the s3c24xx_uart_port is left half-configured
>> (e.g. port->mapbase is set, clk contains ERR_PTR).  On next re-probe,
>> the function s3c24xx_serial_init_port() will exit early with success
>> because of configured port->mapbase and driver will use old values,
>> including the ERR_PTR as clock.
>>
>> Fix this by cleaning the port->mapbase on error path so each re-probe
>> will initialize all of the port settings.
>>
>> Fixes: 60e93575476f ("serial: samsung: enable clock before clearing pending interrupts during init")
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>>
>> ---
>>
>
> Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
> Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>

Tested-by: Kevin Hilman <khilman@baylibre.com>

I verified that this patch fixes a the boot regression I found in
linux-next on the exynos5410-odroidxu.

Thanks,

Kevin