Re: [REVIEW][PATCH 5/5] mnt: Add tests for unprivileged remount cases that have found to be faulty

[Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>]

Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
> Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org> writes:
> 
> > Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
> >> 
> >> Kenton Varda <kenton-AuYgBwuPrUQTaNkGU808tA@public.gmane.org> discovered that by remounting a
> >> read-only bind mount read-only in a user namespace the
> >> MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
> >> to the remount a read-only mount read-write.
> >> 
> >> Upon review of the code in remount it was discovered that the code allowed
> >> nosuid, noexec, and nodev to be cleared.  It was also discovered that
> >> the code was allowing the per mount atime flags to be changed.
> >> 
> >> The first naive patch to fix these issues contained the flaw that using
> >> default atime settings when remounting a filesystem could be disallowed.
> >> 
> >> To avoid this problems in the future add tests to ensure unprivileged
> >> remounts are succeeding and failing at the appropriate times.
> >> 
> >> Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> >
> > one nit below
> >
> > Acked-by: Serge E. Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>
> 
> >> +#ifndef CLONE_NEWSNS
> >
> > Could cause build error in some places...  missspelled NEW S NS above.
> >
> >> +# define CLONE_NEWNS 0x00020000
> >> +#endif
> 
> You are right that is an embarrassing typo.  I wonder how that ever
> happened.  I will take care of that.

Bah, trivially easy to type, hard to spot, and won't break build in most
cases.

-serge