linux-kernel - Re: [PATCH] serial: 8250: Fix serial8250 initialization crash

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Date:   Thu, 17 Jan 2019 19:49:53 +0000
From:   Darwin Dingel <Darwin.Dingel@...iedtelesis.co.nz>
To:     "zhe.he@...driver.com" <zhe.he@...driver.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "Jisheng.Zhang@...aptics.com" <Jisheng.Zhang@...aptics.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250: Fix serial8250 initialization crash

On 17/01/19 10:00 PM, zhe.he@...driver.com wrote:
> From: He Zhe <zhe.he@...driver.com>
> 
> The initialization code of interrupt backoff work might reference NULL
> pointer and cause the following crash, if no port was found.
> 
> [   10.017727] CPU 0 Unable to handle kernel paging request at virtual address 000001b0, epc == 807088e0, ra == 8070863c
> ---- snip ----
> [   11.704470] [<807088e0>] serial8250_register_8250_port+0x318/0x4ac
> [   11.747251] [<80708d74>] serial8250_probe+0x148/0x1c0
> [   11.789301] [<80728450>] platform_drv_probe+0x40/0x94
> [   11.830515] [<807264f8>] really_probe+0xf8/0x318
> [   11.870876] [<80726b7c>] __driver_attach+0x110/0x12c
> [   11.910960] [<80724374>] bus_for_each_dev+0x78/0xcc
> [   11.951134] [<80725958>] bus_add_driver+0x200/0x234
> [   11.989756] [<807273d8>] driver_register+0x84/0x148
> [   12.029832] [<80d72f84>] serial8250_init+0x138/0x198
> [   12.070447] [<80100e6c>] do_one_initcall+0x5c/0x2a0
> [   12.110104] [<80d3a208>] kernel_init_freeable+0x370/0x484
> [   12.150722] [<80a49420>] kernel_init+0x10/0xf8
> [   12.191517] [<8010756c>] ret_from_kernel_thread+0x14/0x1c
> 
> This patch makes sure the initialization code can be reached only if a port
> is found.
> 
> Fixes: commit 6d7f677a2afa ("serial: 8250: Rate limit serial port rx interrupts during input overruns")
> Signed-off-by: He Zhe <zhe.he@...driver.com>
> ---
>   drivers/tty/serial/8250/8250_core.c | 17 +++++++++--------
>   1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 189ab12..e441221 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -1070,15 +1070,16 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
>   
>   			ret = 0;
>   		}
> -	}
>   
> -	/* Initialise interrupt backoff work if required */
> -	if (up->overrun_backoff_time_ms > 0) {
> -		uart->overrun_backoff_time_ms = up->overrun_backoff_time_ms;
> -		INIT_DELAYED_WORK(&uart->overrun_backoff,
> -				  serial_8250_overrun_backoff_work);
> -	} else {
> -		uart->overrun_backoff_time_ms = 0;
> +		/* Initialise interrupt backoff work if required */
> +		if (up->overrun_backoff_time_ms > 0) {
> +			uart->overrun_backoff_time_ms =
> +				up->overrun_backoff_time_ms;
> +			INIT_DELAYED_WORK(&uart->overrun_backoff,
> +					serial_8250_overrun_backoff_work);
> +		} else {
> +			uart->overrun_backoff_time_ms = 0;
> +		}
>   	}
>   
>   	mutex_unlock(&serial_mutex);
> 

Reviewed-by: Darwin Dingel <darwin.dingel@...iedtelesis.co.nz>

I presume this is the same issue reported here:

https://www.spinics.net/lists/linux-serial/msg33114.html
https://lkml.org/lkml/2018/12/22/171



Thanks!
Regards,

Darwin