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Subject: Re: [PATCH 1/2] gpio: gpio-grgpio: fix possible
 sleep-in-atomic-context bugs in grgpio_remove()
To:     Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        linux-gpio <linux-gpio@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20191218132551.10537-1-baijiaju1990@gmail.com>
 <CAMpxmJXZKZYg_B_EpGbnoCEfdKw756KF5gurC4ck6RwjNd7A-g@mail.gmail.com>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <d315dba3-19b9-d860-e557-d083efd9127d@gmail.com>
Date:   Thu, 19 Dec 2019 20:35:58 +0800
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On 2019/12/19 19:10, Bartosz Golaszewski wrote:
> śr., 18 gru 2019 o 14:26 Jia-Ju Bai <baijiaju1990@gmail.com> napisał(a):
>> The driver may sleep while holding a spinlock.
>> The function call path (from bottom to top) in Linux 4.19 is:
>>
>> drivers/gpio/gpiolib-sysfs.c, 796:
>>          mutex_lock in gpiochip_sysfs_unregister
>> drivers/gpio/gpiolib.c, 1455:
>>          gpiochip_sysfs_unregister in gpiochip_remove
>> drivers/gpio/gpio-grgpio.c, 460:
>>          gpiochip_remove in grgpio_remove
>> drivers/gpio/gpio-grgpio.c, 449:
>>          _raw_spin_lock_irqsave in grgpio_remove
>>
>> kernel/irq/irqdomain.c, 243:
>>          mutex_lock in irq_domain_remove
>> drivers/gpio/gpio-grgpio.c, 463:
>>          irq_domain_remove in grgpio_remove
>> drivers/gpio/gpio-grgpio.c, 449:
>>          _raw_spin_lock_irqsave in grgpio_remove
>>
>> mutex_lock() can sleep at runtime.
>>
>> To fix these bugs, gpiochip_remove() and irq_domain_remove() are called
>> without holding the spinlock.
>>
>> These bugs are found by a static analysis tool STCheck written by myself.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
>> ---
>>   drivers/gpio/gpio-grgpio.c      | 5 ++++-
>>   sound/soc/sti/uniperif_player.c | 3 ++-
>>   2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
>> index 08234e64993a..60a2871c5ba7 100644
>> --- a/drivers/gpio/gpio-grgpio.c
>> +++ b/drivers/gpio/gpio-grgpio.c
>> @@ -448,13 +448,16 @@ static int grgpio_remove(struct platform_device *ofdev)
>>                  }
>>          }
>>
>> +       spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
>> +
>>          gpiochip_remove(&priv->gc);
>>
>>          if (priv->domain)
>>                  irq_domain_remove(priv->domain);
>>
>>   out:
>> -       spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
>> +       if (ret)
>> +               spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
> In general there is no need for locking in remove() callbacks. I guess
> you can safely remove the spinlock here all together.

Okay, I will send a new patch.

>
>>          return ret;
>>   }
>> diff --git a/sound/soc/sti/uniperif_player.c b/sound/soc/sti/uniperif_player.c
>> index 48ea915b24ba..62244e207679 100644
>> --- a/sound/soc/sti/uniperif_player.c
>> +++ b/sound/soc/sti/uniperif_player.c
>> @@ -601,13 +601,14 @@ static int uni_player_ctl_iec958_put(struct snd_kcontrol *kcontrol,
>>          mutex_unlock(&player->ctrl_lock);
>>
>>          spin_lock_irqsave(&player->irq_lock, flags);
>> +       spin_unlock_irqrestore(&player->irq_lock, flags);
> Yeah I can tell this was generated automatically - what does this line
> is expected to achieve?

Ah, sorry, this is my mistake.
I forgot to reset the kernel code before writing the patch...


Best wishes,
Jia-Ju Bai