Re: git: 29af6d2e2ec9 - main - msdosfs: replace '/' in direntries with '?'

On Fri, Jul 18, 2025 at 4:42 PM Konstantin Belousov <kostikbel@gmail.com>
wrote:

> On Fri, Jul 18, 2025 at 10:06:56AM -0600, Alan Somers wrote:
> > Should we move this logic up into kern_getdirentries?  msdosfs is not the
> > only file system vulnerable to this problem.
> It is relatively hard to do in kern_getdirentries(), and perhaps would
> cause a severe performance hit for filesystems that do not need it.
>
> The issue is that uio might be for UIO_USERSPACE (and less likely
> UIO_NOCOPY).
> So we must allocate the transient buffer, then call VOP_READDIR() for that
> buffer, then do the validation, and then copyout to the final uio.
>
> Another thing, there are more VOP_READDIR() uses than only
> kern_getdirents().
> Worst part, we do trust UFS and ZFS which are the most perf-sensitive.
>
> I did looked at generic checker, might be guided by some MNTK_-level flag,
> but decided to just patch msdosfs.
>
>
That explanation makes sense.  I guess I need to patch fusefs, too.  We
definitely don't want to trust that one.