[pbs-devel] [PATCH proxmox-backup v4 1/2] fix #5439: allow to reuse existing datastore

[Wolfgang Bumiller]

On Thu, Aug 29, 2024 at 10:12:42AM GMT, Gabriel Goller wrote:
> On 28.08.2024 15:48, Wolfgang Bumiller wrote:
> > On Wed, Aug 14, 2024 at 10:57:11AM GMT, Gabriel Goller wrote:
> > > [skip]
> > >      /// Opens the chunk store with a new process locker.
> > >      ///
> > >      /// Note that this must be used with care, as it's dangerous to create two instances on the
> > >      /// same base path, as closing the underlying ProcessLocker drops all locks from this process
> > >      /// on the lockfile (even if separate FDs)
> > > -    pub(crate) fn open<P: Into<PathBuf>>(
> > > +    pub fn open<P: Into<PathBuf>>(
> > 
> > ^ This is not used and should be dropped.
> 
> Correct, no idea why I did this.
> 
> > > [skip]
> > > +    /// Checks permissions and owner of passed path.
> > > +    fn check_permissions<T: AsRef<Path>>(path: T, file_mode: u32) -> Result<(), Error> {
> > > +        match nix::sys::stat::stat(path.as_ref()) {
> > > +            Ok(stat) => {
> > > +                if stat.st_uid != u32::from(pbs_config::backup_user()?.uid)
> > > +                    || stat.st_gid != u32::from(pbs_config::backup_group()?.gid)
> > > +                    || stat.st_mode & 0o700 != file_mode
> > 
> > Either be exact:
> >    st_mode != file_mode
> > 
> > or only check the required bits:
> >    (st_mode & file_mode) != file_mode
> > 
> > (This is one of those rare cases where I'd rather go with the first
> > option. If users modified the permissions via the shell, they can just
> > fix them up, too.)
> > 
> > as your current code would for instance fail if the lock file had *more*
> > permissions for the *user* (u+x) but would ignore more permissions for
> > *others* (o+rwx or g+w).
> 
> Hmm locally I actually have:
> 
>     || stat.st_mode & 0o770 < file_mode
> 
> with file_mode being 0o640.
> I forgot to add this hunk to the commit :)
> 
> Let me know if this is better or if I should revert to your exact
> match (st_mode != file_mode).

The exact one makes more sense to me. Consider that `0o100 > 0x007`
while `0o007` grants *more* permissions.