Re: Changes to the filesystem while find is running - comments?

[psz () maths usyd edu au (Paul Szabo)]

James,

> >   PARENT=stat(".");
> >   SUBDIR=stat("subdir");
> >   chdir("subdir");
> >   DOT=stat(".");
> >   if (SUBDIR != DOT) {
> >     Print warning message    /*[1]*/
> >   }
> >   else {
> >     Go on with find (recurse)
> >   }
> >   chdir("..");
> >   DOT=stat(".");
> >   if (PARENT != DOT) {
> >     Print message
> >     Exit with fatal error
> >   }
>
> Certainly.  In fact it's how GNU findutils is implemented, except for
> the fact that the "warning message" is a fatal error in GNU findutils
> releases up to and including 4.2.5.  In later versions (we're
> currently at 4.2.7 on ftp://alpha.gnu.org/gnu/findutils) a hack was
> introduced to try to support a special case which works when we've
> traversed an automount mount point on Solaris).

So, you already do the "where did I get back to after chdir(..)" check?

> This algorithm is certainly robust, but it will never descend into an
> automount directory hierarchy.  Do you think we can do better than
> that without opening the door to more exploits?

Hmm... It would not descend into just-now-changed automounts (and it may
not be able to get back out of them), but it should be able to traverse
reasonably long-lived mounts.

Cheers,

Paul Szabo - psz () maths usyd edu au  http://www.maths.usyd.edu.au:8000/u/psz/
School of Mathematics and Statistics  University of Sydney   2006  Australia