Re: [PATCH v3] fs: allow protected cross-uid sticky symlinks

[Al Viro]

On Tue, Jun 01, 2010 at 02:07:34PM -0700, Kees Cook wrote:
> > I don't buy it.  If we are concerned about the symlinks in the middle of
> > pathname, your checks are useless (mkdir /tmp/a, ln -s whatever /tmp/a/b,
> > have victim open /tmp/a/b/something).  If we are not, then your checks are
> > in the wrong place.
> 
> Well, that's not traditionally where the problems happen, but I have no
> problem strengthening the protection to include a full examination of the
> entire path looking for sticky/world-writable directories.
> 
> If not, what is the right place for the checks?

Handling of trailing symlink on open().  At most.  And I wouldn't be
surprised if the real answer turns out to include "... if we have
O_CREAT in flags", but that needs to be determined.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/