linux-kernel - Re: [PATCH v2 3/5] HID: dualsense_remove: manually unregister leds

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Message-ID: <20230209085940.53mrapggf6nagkdh@mail.corp.redhat.com>
Date:   Thu, 9 Feb 2023 09:59:40 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Pietro Borrello <borrello@...g.uniroma1.it>
Cc:     Jiri Kosina <jikos@...nel.org>, Hanno Zulla <kontakt@...no.de>,
        Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Roderick Colenbrander <roderick.colenbrander@...y.com>,
        Sven Eckelmann <sven@...fation.org>,
        linux-leds@...r.kernel.org,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jkl820.git@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiri Kosina <jkosina@...e.cz>,
        Roderick Colenbrander <roderick@...kai.com>
Subject: Re: [PATCH v2 3/5] HID: dualsense_remove: manually unregister leds

On Jan 31 2023, Pietro Borrello wrote:
> Unregister the LED controllers before device removal, to prevent
> unnecessary runs of dualsense_player_led_set_brightness().
> 
> Fixes: 8c0ab553b072 ("HID: playstation: expose DualSense player LEDs through LED class.")
> Signed-off-by: Pietro Borrello <borrello@...g.uniroma1.it>
> 
> ---
> 
> Contrary to the other patches in this series, failing to unregister
> the led controller does not results into a use-after-free thanks
> to the output_worker_initialized variable and the spinlock checks.

And so we don't need that patch (nor for hid-sony.c) because we have a
guard against scheduling a worker job when the device is being removed.

So please drop 3,4,5 from this series, they are just making the code
worse.

Cheers,
Benjamin

> 
> Changes in v2:
> - Unregister multicolor led controller
> - Clarify UAF
> - Link to v1: https://lore.kernel.org/all/20230125-hid-unregister-leds-v1-3-9a5192dcef16@diag.uniroma1.it/
> ---
>  drivers/hid/hid-playstation.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/hid/hid-playstation.c b/drivers/hid/hid-playstation.c
> index 27c40894acab..f23186ca2d76 100644
> --- a/drivers/hid/hid-playstation.c
> +++ b/drivers/hid/hid-playstation.c
> @@ -1503,11 +1503,17 @@ static void dualsense_remove(struct ps_device *ps_dev)
>  {
>  	struct dualsense *ds = container_of(ps_dev, struct dualsense, base);
>  	unsigned long flags;
> +	int i;
>  
>  	spin_lock_irqsave(&ds->base.lock, flags);
>  	ds->output_worker_initialized = false;
>  	spin_unlock_irqrestore(&ds->base.lock, flags);
>  
> +	for (i = 0; i < ARRAY_SIZE(ds->player_leds); i++)
> +		devm_led_classdev_unregister(&ps_dev->hdev->dev, &ds->player_leds[i]);
> +
> +	devm_led_classdev_multicolor_unregister(&ps_dev->hdev->dev, &ds->lightbar);
> +
>  	cancel_work_sync(&ds->output_worker);
>  }
>  
> 
> -- 
> 2.25.1