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SubjectRe: [PATCH v6 02/16] chardev: introduce cdev_get_by_path()
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>>>>>> Why do you have a "string" within the kernel and are not using the
>>>>>> normal open() call from userspace on the character device node on the
>>>>>> filesystem in your namespace/mount/whatever?
>>>>>
>>>>> NVMe-OF is configured using configfs. The target is specified by the
>>>>> user writing a path to a configfs attribute. This is the way it works
>>>>> today but with blkdev_get_by_path()[1]. For the passthru code, we need
>>>>> to get a nvme_ctrl instead of a block_device, but the principal is the same.
>>>>
>>>> Why isn't a fd being passed in there instead of a random string?
>>>
>>> I wouldn't know the answer to this but I assume because once we decided
>>> to use configfs, there was no way for the user to pass the kernel an fd.
>>
>> That's definitely not changing. But this is not different than how we
>> use the block device or file configuration, this just happen to need the
>> nvme controller chardev now to issue I/O.
>
> So, as was kind of alluded to in another part of the thread, what are
> you doing about permissions? It seems that any user/group permissions
> are out the window when you have the kernel itself do the opening of the
> char device, right? Why is that ok? You can pass it _any_ character
> device node and away it goes? What if you give it a "wrong" one? Char
> devices are very different from block devices this way.

We could condition any configfs operation on capable(CAP_NET_ADMIN) to
close that hole for now..

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