Re: [PATCH 1/2] gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio_remove()

[Jia-Ju Bai]

On 2019/12/19 19:10, Bartosz Golaszewski wrote:
> År., 18 gru 2019 o 14:26 Jia-Ju Bai <baijiaju1990@xxxxxxxxx> napisaÅ(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@xxxxxxxxx>
> > ---
> >   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