On Thu, Apr 9, 2015 at 1:31 AM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > > After the last round of feedback I sat down and played with my fix > for the fact that a strategically placed rename, ".." on bind mounts > go up past the root of the bind mount. > > The code better handles the escaped directory returning into it's bind > mount, and is now roughly a constant factor cost in all cases from what > the code costs without the fix. > > So I think I have found a better tradeoff between fixing this bug and > not slowing down path name lookups in the common case. Maybe I'm missing something, but I see a much simpler fix: - When following ".." first just check against the dentry being equal to the root dentry. - If so, then check mount being equal to root mount. - If so, then we are fine, found the root. - If mount is not root mount, then we either have a bind mount or the escape scenario. So have a peek at the mount tree to see if we have a chance of reaching root or not. - If yes, then we are fine, continue upward. - Otherwise stop here and act like we found root. This doesn't have to hook into d_move() and will only trigger the "violated" mode on an very specific and rare case. I haven't thought about this very hard, but I don't see how the root dentry could be avoided without first having access to something outside the root. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
