linux-kernel - Re: [PATCH] tty: serial: add missing pci_dev

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Date:   Tue, 15 Feb 2022 08:46:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Qing Wang <wangqing@...o.com>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: serial: add missing pci_dev_put() before return

On Mon, Feb 14, 2022 at 06:01:12PM -0800, Qing Wang wrote:
> From: Wang Qing <wangqing@...o.com>
> 
> pci_get_slot() increases its reference count, the caller must
> decrement the reference count by calling pci_dev_put()
> 
> Signed-off-by: Wang Qing <wangqing@...o.com>
> ---
>  drivers/tty/serial/pch_uart.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
> index f0351e6..da5a276
> --- a/drivers/tty/serial/pch_uart.c
> +++ b/drivers/tty/serial/pch_uart.c
> @@ -723,7 +723,7 @@ static void pch_request_dma(struct uart_port *port)
>  	if (!chan) {
>  		dev_err(priv->port.dev, "%s:dma_request_channel FAILS(Tx)\n",
>  			__func__);
> -		return;
> +		goto out;
>  	}
>  	priv->chan_tx = chan;
>  
> @@ -739,13 +739,16 @@ static void pch_request_dma(struct uart_port *port)
>  			__func__);
>  		dma_release_channel(priv->chan_tx);
>  		priv->chan_tx = NULL;
> -		return;
> +		goto out;
>  	}
>  
>  	/* Get Consistent memory for DMA */
>  	priv->rx_buf_virt = dma_alloc_coherent(port->dev, port->fifosize,
>  				    &priv->rx_buf_dma, GFP_KERNEL);
>  	priv->chan_rx = chan;
> +
> +out:
> +	pci_dev_put(dma_dev);
>  }
>  
>  static void pch_dma_rx_complete(void *arg)
> -- 
> 2.7.4
> 

What tool are you using to find these?  As Jiri points out, it is not
very correct at all, be careful to not cause bugs when you are
attempting to fix them.

For stuff like this, please always test your changes to verify they
work.

thanks,

greg k-h