Date:	Mon, 20 May 2013 00:39:17 +0000 (GMT)
From:	Jingoo Han <jg1.han@...sung.com>
To:	Timo Ter?s <timo.teras@....fi>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Timo Ter?s <timo.teras@....f>,
	Jingoo Han <jg1.han@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Raphael Assenat <raph@...com>,
	Trent Piepho <tpiepho@...escale.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Arnaud Patard <arnaud.patard@...-net.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Subject: Re: [PATCH] leds: leds-gpio: reserve gpio before using it

Friday, May 17, 2013 4:49 PM, Timo Teras wrote:
> 
> This reverts commit a99d76f (leds: leds-gpio: use gpio_request_one)
> and commit 2d7c22f (leds: leds-gpio: set devm_gpio_request_one()
> flags param correctly) which was a fix of the first one.
> 
> The conversion to devm_gpio_request in commit e3b1d44c (leds:
> leds-gpio: use devm_gpio_request_one) is not reverted.
> 
> The problem is that gpio_cansleep() and gpio_get_value_cansleep()
> calls can crash if the gpio is not first reserved. Incidentally this
> same bug existed earlier and was fixed similarly in commit d95cbe61
> (leds: Fix potential leds-gpio oops). But the OOPS is real. It happens
> when GPIOs are provided by module which is not yet loaded.
> 
> So this fixes the following BUG during my ALIX boot (3.9.2-vanilla):
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000004c
> IP: [<c11287d6>] __gpio_cansleep+0xe/0x1a
> *pde = 00000000
> Oops: 0000 [#1] SMP
> Modules linked in: leds_gpio(+) via_rhine mii cs5535_mfd mfd_core
> geode_rng rng_core geode_aes isofs nls_utf8 nls_cp437 vfat fat
> ata_generic pata_amd pata_cs5536 pata_acpi libata ehci_pci ehci_hcd
> ohci_hcd usb_storage usbcore usb_common sd_mod scsi_mod squashfs loop
> Pid: 881, comm: modprobe Not tainted 3.9.2 #1-Alpine
> EIP: 0060:[<c11287d6>] EFLAGS: 00010282 CPU: 0
> EIP is at __gpio_cansleep+0xe/0x1a
> EAX: 00000000 EBX: cf364018 ECX: c132b8b9 EDX: 00000000
> ESI: c13993a4 EDI: c1399370 EBP: cded9dbc ESP: cded9dbc
>  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> CR0: 8005003b CR2: 0000004c CR3: 0f0c4000 CR4: 00000090
> DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> DR6: ffff0ff0 DR7: 00000400
> Process modprobe (pid: 881, ti=cded8000 task=cf094aa0 task.ti=cded8000)
> Stack:
>  cded9de0 d09471cb 00000000 c1399260 cf364014 00000000 c1399260 c1399254
>  d0949014 cded9df4 c118cd59 c1399260 d0949014 d0949014 cded9e08 c118ba47
>  c1399260 d0949014 c1399294 cded9e1c c118bb75 cded9e24 d0949014 00000000
> Call Trace:
>  [<d09471cb>] gpio_led_probe+0xba/0x203 [leds_gpio]
>  [<c118cd59>] platform_drv_probe+0x26/0x48
>  [<c118ba47>] driver_probe_device+0x75/0x15c
>  [<c118bb75>] __driver_attach+0x47/0x63
>  [<c118a727>] bus_for_each_dev+0x3c/0x66
>  [<c118b6f9>] driver_attach+0x14/0x16
>  [<c118bb2e>] ? driver_probe_device+0x15c/0x15c
>  [<c118b3d5>] bus_add_driver+0xbd/0x1bc
>  [<d08b4000>] ? 0xd08b3fff
>  [<d08b4000>] ? 0xd08b3fff
>  [<c118bffc>] driver_register+0x74/0xec
>  [<d08b4000>] ? 0xd08b3fff
>  [<c118c8e8>] platform_driver_register+0x38/0x3a
>  [<d08b400d>] gpio_led_driver_init+0xd/0x1000 [leds_gpio]
>  [<c100116c>] do_one_initcall+0x6b/0x10f
>  [<d08b4000>] ? 0xd08b3fff
>  [<c105e918>] load_module+0x1631/0x1907
>  [<c10975d6>] ? insert_vmalloc_vmlist+0x14/0x43
>  [<c1098d5b>] ? __vmalloc_node_range+0x13e/0x15f
>  [<c105ec50>] sys_init_module+0x62/0x77
>  [<c1257888>] syscall_call+0x7/0xb
> EIP: [<c11287d6>] __gpio_cansleep+0xe/0x1a SS:ESP 0068:cded9dbc
> CR2: 000000000000004c
>  ---[ end trace 5308fb20d2514822 ]---
> 
> Signed-off-by: Timo Ter?s <timo.teras@....f>
> Cc: Jingoo Han <jg1.han@...sung.com>

Acked-by: Jingoo Han <jg1.han@...sung.com>

I look at what happens in leds-gpio.
As you mentioned, devm_gpio_request() should be called before
gpio_cansleep() and gpio_get_value_cansleep are called.
Thank you for sending the patch.

Best regards,
Jingoo Han

> Cc: Sachin Kamat <sachin.kamat@...aro.org>
> Cc: Raphael Assenat <raph@...com>
> Cc: Trent Piepho <tpiepho@...escale.com>
> Cc: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> Cc: Arnaud Patard <arnaud.patard@...-net.org>
> Cc: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
> ---
>  drivers/leds/leds-gpio.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
> index a0d931b..b02b679 100644
> --- a/drivers/leds/leds-gpio.c
> +++ b/drivers/leds/leds-gpio.c
> @@ -107,6 +107,10 @@ static int create_gpio_led(const struct gpio_led *template,
>  		return 0;
>  	}
> 
> +	ret = devm_gpio_request(parent, template->gpio, template->name);
> +	if (ret < 0)
> +		return ret;
> +
>  	led_dat->cdev.name = template->name;
>  	led_dat->cdev.default_trigger = template->default_trigger;
>  	led_dat->gpio = template->gpio;
> @@ -126,10 +130,7 @@ static int create_gpio_led(const struct gpio_led *template,
>  	if (!template->retain_state_suspended)
>  		led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
> 
> -	ret = devm_gpio_request_one(parent, template->gpio,
> -				    (led_dat->active_low ^ state) ?
> -				    GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW,
> -				    template->name);
> +	ret = gpio_direction_output(led_dat->gpio, led_dat->active_low ^ state);
>  	if (ret < 0)
>  		return ret;
> 
> --
> 1.8.2.3
> 

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