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SubjectRe: [PATCH v3] leds: Introduce userspace leds driver
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On 09/16/2016 07:50 AM, Pavel Machek wrote:
> Hi!
>
>>>>>> + if (copy_from_user(&udev->user_dev, buffer,
>>>>>> + sizeof(struct uleds_user_dev))) {
>>>>>> + ret = -EFAULT;
>>>>>> + goto out;
>>>>>> + }
>>>>>> +
>>>>>> + if (!udev->user_dev.name[0]) {
>>>>>> + ret = -EINVAL;
>>>>>> + goto out;
>>>>>> + }
>>>>>> +
>>>>>> + ret = led_classdev_register(NULL, &udev->led_cdev);
>>>>>> + if (ret < 0)
>>>>>> + goto out;
>>>>
>>>> No sanity checking on the name -> probably a security hole. Do not
>>>> push this upstream before this is fixed.
>>>
>>
>> If this is a serious security issue, then you should also raise an issue
>> with input maintainers because this is the extent of sanity checking for
>> uinput device names as well.
>
> I guess that should be fixed. But lets not add new ones.
>
>> I must confess that I am no security expert, so unless you can give specific
>> examples of what potential threats are, I will not be able to guess what I
>> need to do to fix it.
>>
>> After some digging around the kernel, I don't see many instances of
>> validating device node names. The best I have found so far comes from
>> create_entry() in binfmt_misc.c
>>
>> if (!e->name[0] ||
>> !strcmp(e->name, ".") ||
>> !strcmp(e->name, "..") ||
>> strchr(e->name, '/'))
>> goto einval;
>>
>> Would something like this be a sufficient sanity check? I suppose we could
>> also check for non-printing characters, but I don't think ignoring them
>> would be a security issue.
>
> That would be minimum, yes. I guess it would be better/easier to just
> limit the names to [a-zA-Z:-_0-9]*?

Right, and we also could check if there are no more then two ":"
characters in the name.

--
Best regards,
Jacek Anaszewski

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