linux-kernel - RE: [PATCH] tty: serial: fsl_lpuart: fix potential bug when using both of_alias_get_id and ida_simple

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Message-ID: <AM9PR04MB8274AA137A140A4B4DFD0EE889169@AM9PR04MB8274.eurprd04.prod.outlook.com>
Date:   Mon, 21 Mar 2022 13:33:24 +0000
From:   Shenwei Wang <shenwei.wang@....com>
To:     Sherry Sun <sherry.sun@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        Vabhav Sharma <vabhav.sharma@....com>
CC:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] tty: serial: fsl_lpuart: fix potential bug when using
 both of_alias_get_id and ida_simple_get



> -----Original Message-----
> From: Sherry Sun <sherry.sun@....com>
> Sent: Monday, March 21, 2022 6:22 AM
> To: gregkh@...uxfoundation.org; jirislaby@...nel.org; Vabhav Sharma
> <vabhav.sharma@....com>
> Cc: linux-serial@...r.kernel.org; linux-kernel@...r.kernel.org; dl-linux-imx
> <linux-imx@....com>
> Subject: [PATCH] tty: serial: fsl_lpuart: fix potential bug when using both
> of_alias_get_id and ida_simple_get
> 
> Now fsl_lpuart driver use both of_alias_get_id() and ida_simple_get() in .probe(),
> which has the potential bug. For example, when remove the
> lpuart7 alias in dts, of_alias_get_id() will return error, then call
> ida_simple_get() to allocate the id 0 for lpuart7, this may confilct with the
> lpuart4 which has alias 0.

The behavior of ida_simple_get() is to allocate an unused alias number. Do you see any conflict when you test?

Regards,
Shenwei

> 
>     aliases {
> 	...
>         serial0 = &lpuart4;
>         serial1 = &lpuart5;
>         serial2 = &lpuart6;
>         serial3 = &lpuart7;
>     }
> 
> So remove the ida_simple_get() in .probe(), return an error directly when calling
> of_alias_get_id() fails, which is consistent with other uart drivers behavior.
> 
> Fixes: 3bc3206e1c0f ("serial: fsl_lpuart: Remove the alias node dependence")
> Signed-off-by: Sherry Sun <sherry.sun@....com>
> ---
>  drivers/tty/serial/fsl_lpuart.c | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index
> 452a015825ba..40465d23d7ad 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -239,8 +239,6 @@
>  /* IMX lpuart has four extra unused regs located at the beginning */
>  #define IMX_REG_OFF	0x10
> 
> -static DEFINE_IDA(fsl_lpuart_ida);
> -
>  enum lpuart_type {
>  	VF610_LPUART,
>  	LS1021A_LPUART,
> @@ -276,7 +274,6 @@ struct lpuart_port {
>  	int			rx_dma_rng_buf_len;
>  	unsigned int		dma_tx_nents;
>  	wait_queue_head_t	dma_wait;
> -	bool			id_allocated;
>  };
> 
>  struct lpuart_soc_data {
> @@ -2716,23 +2713,18 @@ static int lpuart_probe(struct platform_device
> *pdev)
> 
>  	ret = of_alias_get_id(np, "serial");
>  	if (ret < 0) {
> -		ret = ida_simple_get(&fsl_lpuart_ida, 0, UART_NR,
> GFP_KERNEL);
> -		if (ret < 0) {
> -			dev_err(&pdev->dev, "port line is full, add device
> failed\n");
> -			return ret;
> -		}
> -		sport->id_allocated = true;
> +		dev_err(&pdev->dev, "failed to get alias id, errno %d\n", ret);
> +		return ret;
>  	}
>  	if (ret >= ARRAY_SIZE(lpuart_ports)) {
>  		dev_err(&pdev->dev, "serial%d out of range\n", ret);
> -		ret = -EINVAL;
> -		goto failed_out_of_range;
> +		return -EINVAL;
>  	}
>  	sport->port.line = ret;
> 
>  	ret = lpuart_enable_clks(sport);
>  	if (ret)
> -		goto failed_clock_enable;
> +		return ret;
>  	sport->port.uartclk = lpuart_get_baud_clk_rate(sport);
> 
>  	lpuart_ports[sport->port.line] = sport; @@ -2781,10 +2773,6 @@ static
> int lpuart_probe(struct platform_device *pdev)
>  failed_attach_port:
>  failed_irq_request:
>  	lpuart_disable_clks(sport);
> -failed_clock_enable:
> -failed_out_of_range:
> -	if (sport->id_allocated)
> -		ida_simple_remove(&fsl_lpuart_ida, sport->port.line);
>  	return ret;
>  }
> 
> @@ -2794,9 +2782,6 @@ static int lpuart_remove(struct platform_device
> *pdev)
> 
>  	uart_remove_one_port(&lpuart_reg, &sport->port);
> 
> -	if (sport->id_allocated)
> -		ida_simple_remove(&fsl_lpuart_ida, sport->port.line);
> -
>  	lpuart_disable_clks(sport);
> 
>  	if (sport->dma_tx_chan)
> @@ -2926,7 +2911,6 @@ static int __init lpuart_serial_init(void)
> 
>  static void __exit lpuart_serial_exit(void)  {
> -	ida_destroy(&fsl_lpuart_ida);
>  	platform_driver_unregister(&lpuart_driver);
>  	uart_unregister_driver(&lpuart_reg);
>  }
> --
> 2.17.1