Re: [PATCH] generic/453: Exclude filenames that are not supported by exfat

[Shreeya Patel <shreeya.patel@collabora.com>]

On 26/04/21 5:27 pm, Shreeya Patel wrote:
>
> On 26/04/21 6:04 am, Matthew Wilcox wrote:
>> On Mon, Apr 26, 2021 at 04:01:05AM +0530, Shreeya Patel wrote:
>>> exFAT filesystem does not support the following character codes
>>> 0x0000 - 0x001F ( Control Codes ), /, ?, :, ", \, *, <, |, >
>> ummm ...
>>
>>> -# Fake slash?
>>> -setf "urk\xc0\xafmoo" "FAKESLASH"
>> That doesn't use any of the explained banned characters.  It uses 0xc0,
>> 0xaf.
>>
>> Now, in utf-8, that's an nonconforming sequence.  "The Unicode and UCS
>> standards require that producers of UTF-8 shall use the shortest form
>> possible, for example, producing a two-byte sequence with first byte 
>> 0xc0
>> is nonconforming.  Unicode 3.1 has added the requirement that conforming
>> programs must not accept non-shortest forms in their input."
>>
>> So is it that exfat is rejecting nonconforming sequences?  Or is it
>> converting the nonconforming sequence from 0xc0 0xaf to the conforming
>> sequence 0x2f, and then rejecting it (because it's '/')?
>>
>
> No, I don't think exfat is not converting nonconforming sequence from 
> 0xc0 0xaf
> to the conforming sequence 0x2f.


Sorry, I meant "I don't think exfat is converting nonconforming sequence 
from 0xc0 0xaf
to the conforming sequence 0x2f." here.


> Because I get different outputs when tried with both ways.
> When I create a file with "urk\xc0\xafmoo", I get output as "Operation 
> not permitted"
> and when I create it as "urk\x2fmoo", it gives "No such file or 
> directory error" or
> you can consider this error as "Invalid argument"
> ( because that's what I get when I try for other characters like |, :, 
> ?, etc )
>
> Box filename also fails with "Invalid argument" error.
>
>