On Sat, Oct 13, 2018 at 07:53:26PM +1100, Aleksa Sarai wrote: > I didn't know about path_is_under() -- I just checked and it appears to > not take &rename_lock? From my understanding, in order to protect > against the rename attack you need to take &rename_lock (or check > against &rename_lock at least and retry if it changed). > > I could definitely use path_is_under() if you prefer, though I think > that in this case we'd need to take &rename_lock (right?). Also is there > a speed issue with taking the write-side of a seqlock when we are just > reading -- is this more efficient than doing a retry like in __d_path? ??? 1) it uses is_subdir(), which does deal with rename_lock 2) what it does is taking mount_lock.lock. I.e. the same thing as the second retry in __d_path(). _If_ it shows up in profiles, we can switch it to read_seqbegin_or_lock(), but I'd like to see the profiling data first.
