linux-kernel - Re: [PATCH] input: psmouse: Add unlock mutex before to exit psmouse_attr_set

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Message-ID: <Zvv0lDZZVDM2CbHf@google.com>
Date: Tue, 1 Oct 2024 06:09:40 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Alessandro Zanni <alessandro.zanni87@...il.com>
Cc: erick.archer@...look.com, zhoubinbin@...ngson.cn, jay_lee@...art.com,
	jon_xie@...art.com, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
	anupnewsmail@...il.com
Subject: Re: [PATCH] input: psmouse: Add unlock mutex before to exit
 psmouse_attr_set_protocol

Hi Alessandro,

On Tue, Oct 01, 2024 at 01:08:38PM +0200, Alessandro Zanni wrote:
> In error handling code for "no such device" or memory already used,
> release the mutex before to return.
> 
> Found with Coccinelle static analisys tool,
> script: https://coccinelle.gitlabpages.inria.fr/website/rules/mut.cocci
> 
> Signed-off-by: Alessandro Zanni <alessandro.zanni87@...il.com>
> ---
>  drivers/input/mouse/psmouse-base.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/input/mouse/psmouse-base.c b/drivers/input/mouse/psmouse-base.c
> index 5a4defe9cf32..cb3a125d8d7c 100644
> --- a/drivers/input/mouse/psmouse-base.c
> +++ b/drivers/input/mouse/psmouse-base.c
> @@ -1930,11 +1930,13 @@ static ssize_t psmouse_attr_set_protocol(struct psmouse *psmouse, void *data, co
>  
>  		if (serio->drv != &psmouse_drv) {
>  			input_free_device(new_dev);
> +			mutex_unlock(&psmouse_mutex);

I am sorry, bit this makes absolutely no sense. This mutex is taken
(and then released) in psmouse_attr_set_helper() wrapper.
psmouse_attr_set_protocol() momentarily drops and then reacquires it,
but it should not release it either failure or success parts.

Thanks.

-- 
Dmitry