Re: [PATCH net-next] net: ethtool: Fix out-of-bounds copy to user

[Ding Hui <dinghui@sangfor.com.cn>]

On 2023/6/2 8:26 下午, Andrew Lunn wrote:
>>> Changing the copy size would not fix this. The problem is the driver
>>> will be overwriting with the size that it thinks it should be using.
>>> Reducing the value that is provided for the memory allocations will
>>> cause the driver to corrupt memory.
>>>
>>
>> I noticed that, in fact I did use the returned length to allocate
>> kernel memory, and only use adjusted length to copy to user.
> 
> This is also something i checked when quickly looking at the patch. It
> does look correct.
> 

Thanks.

> Also, RTNL should be held during the time both calls are made into the
> driver. So nothing from userspace should be able to get in the middle
> of these calls to change the number of queues.
> 

The RTNL lock is already be held during every each ioctl in dev_ethtool().

     rtnl_lock();
     rc = __dev_ethtool(net, ifr, useraddr, ethcmd, state);
     rtnl_unlock();

-- 
Thanks,
-dinghui