linux-kernel - Re: [PATCH V3 1/2] serial: sprd: Assign sprd_port after initialized to avoid wrong access

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Date:   Tue, 25 Jul 2023 08:50:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chunyan Zhang <chunyan.zhang@...soc.com>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 1/2] serial: sprd: Assign sprd_port after initialized
 to avoid wrong access

On Tue, Jul 25, 2023 at 02:40:52PM +0800, Chunyan Zhang wrote:
> The global pointer 'sprd_port' may not zero when sprd_probe returns
> failure, that is a risk for sprd_port to be accessed afterward, and
> may lead to unexpected errors.
> 
> For example:
> 
> There are two UART ports, UART1 is used for console and configured in
> kernel command line, i.e. "console=";
> 
> The UART1 probe failed and the memory allocated to sprd_port[1] was
> released, but sprd_port[1] was not set to NULL;
> 
> In UART2 probe, the same virtual address was allocated to sprd_port[2],
> and UART2 probe process finally will go into sprd_console_setup() to
> register UART1 as console since it is configured as preferred console
> (filled to console_cmdline[]), but the console parameters (sprd_port[1])
> belong to UART2.
> 
> So move the sprd_port[] assignment to where the port already initialized
> can avoid the above issue.
> 
> Fixes: b7396a38fb28 ("tty/serial: Add Spreadtrum sc9836-uart driver support")
> Signed-off-by: Chunyan Zhang <chunyan.zhang@...soc.com>
> ---
> V3:
> - Call uart_unregister_driver() only when the 'sprd_ports_num' decreases to 0;
> - Add calling sprd_rx_free_buf() instread of sprd_remove() under clean_up lable. 
> 
> V2:
> - Leave sprd_remove() to keep the unrelated code logic the same.
> ---
>  drivers/tty/serial/sprd_serial.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> index b58f51296ace..fc1377029021 100644
> --- a/drivers/tty/serial/sprd_serial.c
> +++ b/drivers/tty/serial/sprd_serial.c
> @@ -1106,7 +1106,7 @@ static bool sprd_uart_is_console(struct uart_port *uport)
>  static int sprd_clk_init(struct uart_port *uport)
>  {
>  	struct clk *clk_uart, *clk_parent;
> -	struct sprd_uart_port *u = sprd_port[uport->line];
> +	struct sprd_uart_port *u = container_of(uport, struct sprd_uart_port, port);

Now that you are not allocaing the sprd_port[] pointers, shouldn't you
also remove that variable entirely?

thanks,

greg k-h