Re: [PATCH] net: seeq: Fix use after free vulnerability in ether3 Driver Due to Race Condition

[Kaixin Wang]

At 2024-09-11 17:29:44, "Przemek Kitszel" <przemyslaw.kitszel@xxxxxxxxx> wrote:
>On 9/9/24 19:58, Kaixin Wang wrote:
>> In the ether3_probe function, a timer is initialized with a callback
>> function ether3_ledoff, bound to &prev(dev)->timer. Once the timer is
>> started, there is a risk of a race condition if the module or device
>> is removed, triggering the ether3_remove function to perform cleanup.
>> The sequence of operations that may lead to a UAF bug is as follows:
>> 
>> CPU0                                    CPU1
>> 
>>                        |  ether3_ledoff
>> ether3_remove         |
>>    free_netdev(dev);   |
>>    put_devic           |
>>    kfree(dev);         |
>>   |  ether3_outw(priv(dev)->regs.config2 |= CFG2_CTRLO, REG_CONFIG2);
>>                        | // use dev
>> 
>> Fix it by ensuring that the timer is canceled before proceeding with
>> the cleanup in ether3_remove.
>
>this code change indeed prevents UAF bug
>but as is, the CFG2_CTRLO flag of REG_CONFIG2 will be left in state "ON"
>
>it would be better to first turn the LED off unconditionally
>

I will fix it in the next version of patch.

>> 
>> Signed-off-by: Kaixin Wang <kxwang23@xxxxxxxxxxxxxx>
>> ---
>>   drivers/net/ethernet/seeq/ether3.c | 1 +
>>   1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/net/ethernet/seeq/ether3.c b/drivers/net/ethernet/seeq/ether3.c
>> index c672f92d65e9..f9d27c9d6808 100644
>> --- a/drivers/net/ethernet/seeq/ether3.c
>> +++ b/drivers/net/ethernet/seeq/ether3.c
>> @@ -850,6 +850,7 @@ static void ether3_remove(struct expansion_card *ec)
>>   	ecard_set_drvdata(ec, NULL);
>>   
>>   	unregister_netdev(dev);
>> +	del_timer_sync(&priv(dev)->timer);
>>   	free_netdev(dev);
>>   	ecard_release_resources(ec);
>>   }
>
>
Thanks for the review!

Best regards,
Kaixin Wang