Re: RFC: checking file systems support UF_HIDDEN, UF_SYSTEM

From: Shawn Webb <shawn.webb_at_hardenedbsd.org>
Date: Wed, 02 Jul 2025 21:05:53 UTC
On Wed, Jul 02, 2025 at 02:02:14PM -0700, Rick Macklem wrote:
> Hi,
> 
> I am implementing the "hidden" and "system" attributes for
> NFSv4 using UF_HIDDEN and UF_SYSTEM.
> 
> In a couple of places in the code, I need to know if a file
> system supports these flags.
> I can think of two ways to do this.
> #1 - Create a new VFCF_HIDSYS flag that is set via VFS_SET()
>        for file systems that support the UF_HIDDEN and UF_SYSTEM
>        flags and test for that flag being set.
> or
> #2 - Write it this way...
>       if (strcmp(vp->v_mount->mnt_vfc->vfc_name, "zfs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "ufs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "msdosfs") != 0 ||
>           strcmp(vp->v_mount->mnt_vfc->vfc_name, "tmpfs") != 0)
> 
> Which do you think is preferable (or do you have another idea)?

I have no skin in the game, but I'm curious if you could tell me more
about UF_HIDDEN. Can you explain what that is or perhaps link me to
some documentation for me to read?

Thanks,

-- 
Shawn Webb
Cofounder / Security Engineer
HardenedBSD

Signal Username:  shawn_webb.74
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