linux-kernel - Re: [PATCH] media: lirc: Fix error handling in lirc

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Message-ID: <Z3u2zVQyammNo_o3@gofer.mess.org>
Date: Mon, 6 Jan 2025 10:56:13 +0000
From: Sean Young <sean@...s.org>
To: Ma Ke <make24@...as.ac.cn>
Cc: mchehab@...nel.org, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] media: lirc: Fix error handling in lirc_register()

Hi,

On Sun, Jan 05, 2025 at 06:01:01PM +0800, Ma Ke wrote:
> When cdev_device_add() failed, calling put_device() to explicitly
> release dev->lirc_dev. Otherwise, it could cause the fault of the
> reference count.
> 
> Found by code review.

Interesting find, thanks for finding and reporting.

So I think the idea is right, but there is a problem. lirc_release_device()
will do a put_device() on the rcdev, but no corresponding get_device() is
done in this code path.


Sean

> 
> Cc: stable@...r.kernel.org
> Fixes: a6ddd4fecbb0 ("media: lirc: remove last remnants of lirc kapi")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  drivers/media/rc/lirc_dev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
> index a2257dc2f25d..ed839e15fa16 100644
> --- a/drivers/media/rc/lirc_dev.c
> +++ b/drivers/media/rc/lirc_dev.c
> @@ -765,6 +765,7 @@ int lirc_register(struct rc_dev *dev)
>  	return 0;
>  
>  out_ida:
> +	put_device(&dev->lirc_dev);
>  	ida_free(&lirc_ida, minor);
>  	return err;
>  }
> -- 
> 2.25.1