linux-kernel - Re: [PATCH] amba: fix refcount underflow if amba_device

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Date:   Mon, 23 May 2022 20:09:41 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>
Cc:     linux@...linux.org.uk, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, robh@...nel.org
Subject: Re: [PATCH] amba: fix refcount underflow if amba_device_add() fails

On Tue, May 24, 2022 at 10:51:39AM +0800, Kefeng Wang wrote:
> "ARM: 9192/1: amba: fix memory leak in amba_device_try_add()" leads
> to a refcount underflow if amba_device_add() fails, which called by
> of_amba_device_create(), the of_amba_device_create() already exists
> the error handling, so amba_put_device() only need to be added into
> amba_deferred_retry().
> 
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>

Tested-by: Guenter Roeck <linux@...ck-us.net>

Thanks,
Guenter

> ---
>  drivers/amba/bus.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index 0e3ed5eb367b..0cb20324da16 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -493,13 +493,8 @@ static int amba_device_try_add(struct amba_device *dev, struct resource *parent)
>  		goto skip_probe;
>  
>  	ret = amba_read_periphid(dev);
> -	if (ret) {
> -		if (ret != -EPROBE_DEFER) {
> -			amba_device_put(dev);
> -			goto err_out;
> -		}
> +	if (ret)
>  		goto err_release;
> -	}
>  
>  skip_probe:
>  	ret = device_add(&dev->dev);
> @@ -546,6 +541,7 @@ static int amba_deferred_retry(void)
>  			continue;
>  
>  		list_del_init(&ddev->node);
> +		amba_device_put(ddev->dev);
>  		kfree(ddev);
>  	}
>  
> -- 
> 2.35.3
>