Re: [Samba] SMB3 Unix Extensions - creating special files

[Jeremy Allison <jra@samba.org>]

On 3/2/26 4:41 PM, Nikkos Svoboda via samba wrote:
> 
>    Jumping in here briefly, I believe the "default" symlink style 
> requested by the client mount options is now "symlink=native", which 
> creates the 0-sized files with extended attributes on the server.
> 
>    I'd also like to know:  Is it intended to allow creation of "actual" 
> symlinks on a supported server filesystem via unix 3.1.1 Extensions? The 
> mount option "symlink=unix" (which creates "actual" symlinks on the 
> server), when used with SMB 3.1.1 unix extensions, causes symlink 
> creation to fail on the client with "Operation not supported" (client 
> kernel 6.17, ubuntu 24.04). That mount option appears to be referred to 
> as "SMB1 unix create symlink command" which I presume means it is 
> limited to the SMB1 unix extensions.
> 
>    The archived e-mail conversation chain here (though it includes some 
> outdated information) helped me to understand some of what the symlink= 
> and reparse= mount options were intended for:
> https://lwn.net/ml/all/20241007183650.aw3skuztljpgk2bs@pali/

The goal (at least when I was involved with this effort) was to
explicitly *ban* SMB3 UNIX extensions ever from creating server-side
symlinks.

Such activities are inherently unsafe and a source of many, many
CVE's.