Re: [PATCH] serial: 8250: Fix serial8250 initialization crash

[Darwin Dingel]

On 18/01/19 8:49 AM, Darwin Dingel wrote:
> On 17/01/19 10:00 PM, zhe.he@xxxxxxxxxxxxx wrote:
>> From: He Zhe <zhe.he@xxxxxxxxxxxxx>
>>
>> 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@xxxxxxxxxxxxx>
>> ---
>>    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@xxxxxxxxxxxxxxxxxxx>
> 
> 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
> 

Adding Colin and Dan.

Regards,
Darwin