linux-kernel - Re: [PATCH v3 1/4] gpio: virtuser: fix missing lookup table cleanups

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Message-ID: <nvhxtxiooepkbrl6duymqzf6rduaebcstvz6vvpi5ft3nnvkzu@vtn5bmlobdfx>
Date: Sat, 4 Jan 2025 00:04:20 +0900
From: Koichiro Den <koichiro.den@...onical.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linus.walleij@...aro.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] gpio: virtuser: fix missing lookup table cleanups

On Fri, Jan 03, 2025 at 03:38:46PM +0100, Bartosz Golaszewski wrote:
> On Fri, Jan 3, 2025 at 3:18 PM Koichiro Den <koichiro.den@...onical.com> wrote:
> >
> > When a virtuser device is created via configfs and the probe fails due
> > to an incorrect lookup table, the table is not removed. This prevents
> > subsequent probe attempts from succeeding, even if the issue is
> > corrected, unless the device is released. Additionally, cleanup is also
> > needed in the less likely case of platform_device_register_full()
> > failure.
> >
> > Besides, a consistent memory leak in lookup_table->dev_id was spotted
> > using kmemleak by toggling the live state between 0 and 1 with a correct
> > lookup table.
> >
> > Introduce gpio_virtuser_remove_lookup_table() as the counterpart to the
> > existing gpio_virtuser_make_lookup_table() and call it from all
> > necessary points to ensure proper cleanup.
> >
> > Fixes: 91581c4b3f29 ("gpio: virtuser: new virtual testing driver for the GPIO API")
> > Signed-off-by: Koichiro Den <koichiro.den@...onical.com>
> > ---
> >  drivers/gpio/gpio-virtuser.c | 36 +++++++++++++++++++++++++-----------
> >  1 file changed, 25 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/gpio/gpio-virtuser.c b/drivers/gpio/gpio-virtuser.c
> > index 91b6352c957c..e89b1239b635 100644
> > --- a/drivers/gpio/gpio-virtuser.c
> > +++ b/drivers/gpio/gpio-virtuser.c
> > @@ -1439,6 +1439,15 @@ gpio_virtuser_make_lookup_table(struct gpio_virtuser_device *dev)
> >         return 0;
> >  }
> >
> > +static void
> > +gpio_virtuser_remove_lookup_table(struct gpio_virtuser_device *dev)
> > +{
> > +       gpiod_remove_lookup_table(dev->lookup_table);
> > +       kfree(dev->lookup_table->dev_id);
> 
> Ah, this has been here all along as well. :/
> 
> 
> > +       kfree(dev->lookup_table);
> > +       dev->lookup_table = NULL;
> > +}
> > +
> >  static struct fwnode_handle *
> >  gpio_virtuser_make_device_swnode(struct gpio_virtuser_device *dev)
> >  {
> > @@ -1487,10 +1496,8 @@ gpio_virtuser_device_activate(struct gpio_virtuser_device *dev)
> >         pdevinfo.fwnode = swnode;
> >
> >         ret = gpio_virtuser_make_lookup_table(dev);
> > -       if (ret) {
> > -               fwnode_remove_software_node(swnode);
> > -               return ret;
> > -       }
> > +       if (ret)
> > +               goto err_remove_swnode;
> >
> >         reinit_completion(&dev->probe_completion);
> >         dev->driver_bound = false;
> > @@ -1498,23 +1505,31 @@ gpio_virtuser_device_activate(struct gpio_virtuser_device *dev)
> >
> >         pdev = platform_device_register_full(&pdevinfo);
> >         if (IS_ERR(pdev)) {
> > +               ret = PTR_ERR(pdev);
> >                 bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
> > -               fwnode_remove_software_node(swnode);
> > -               return PTR_ERR(pdev);
> > +               goto err_remove_lookup_table;
> >         }
> >
> >         wait_for_completion(&dev->probe_completion);
> >         bus_unregister_notifier(&platform_bus_type, &dev->bus_notifier);
> >
> >         if (!dev->driver_bound) {
> > -               platform_device_unregister(pdev);
> > -               fwnode_remove_software_node(swnode);
> > -               return -ENXIO;
> > +               ret = -ENXIO;
> > +               goto err_unregister_pdev;
> >         }
> >
> >         dev->pdev = pdev;
> >
> >         return 0;
> > +
> > +err_unregister_pdev:
> > +       platform_device_unregister(pdev);
> > +err_remove_lookup_table:
> > +       gpio_virtuser_remove_lookup_table(dev);
> > +err_remove_swnode:
> > +       fwnode_remove_software_node(swnode);
> > +
> > +       return ret;
> >  }
> >
> >  static void
> > @@ -1526,10 +1541,9 @@ gpio_virtuser_device_deactivate(struct gpio_virtuser_device *dev)
> >
> >         swnode = dev_fwnode(&dev->pdev->dev);
> >         platform_device_unregister(dev->pdev);
> > +       gpio_virtuser_remove_lookup_table(dev);
> 
> Any reason for moving it earlier?

Just to make the resources teardown order more natural and better align
with the error path in gpio_virtuser_device_activate() (i.e., the new goto
labels part I added). IIUC, it can be safely moved as such under dev->lock.

Thanks.

-Koichiro

> 
> Bart
> 
> >         fwnode_remove_software_node(swnode);
> >         dev->pdev = NULL;
> > -       gpiod_remove_lookup_table(dev->lookup_table);
> > -       kfree(dev->lookup_table);
> >  }
> >
> >  static ssize_t
> > --
> > 2.43.0
> >