[Samba] FreeBSD samba server returns nt_status_acces_denied when DosStream xattr larger than 64KB

Andrew Walker walker.aj325 at gmail.com
Tue Aug 8 01:26:22 UTC 2017

It's also interesting to note that ReFS in windows has a 128KB limit on the
size of alternate data streams.

When you try to write an overly large stream, the ReFS-backed server
replies with "NT_STATUS_FILE_SYSTEM_LIMITATION" (0xc0000427) rather than
"access denied". The windows client handles this more gracefully than a
simple access denied message. It allows users to skip the file / doesn't
pop up a password prompt.

On Mon, Aug 7, 2017 at 6:15 AM, Andrew Walker <walker.aj325 at gmail.com>

> If you feel like it, you could write a VFS module that adds better support
>> for
>> this on FreeBSD, but what is the use case?
> I've noticed in online forums that occasionally home NAS users will for
> various reasons have streams_xattr enabled and receive 'access denied'
> errors when trying to write files with large alternate datastreams. These
> are typically on media files (most commonly I've seen them on .avi files),
> but I haven't looked closely at them. I'd say the large ADS is either
> metadata or malware :-)
> The issue doesn't come up frequently because most people don't enable
> streams_xattr (though this may change as more home users or NAS vendors
> start enabling vfs_fruit + streams_xattr).
> I was just curious about whether the behavior is configurable, and now the
> curiosity is satisfied. :-)

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