Messages in this thread | | | Date | Sat, 13 Oct 2018 10:04:32 +0100 | From | Al Viro <> | Subject | Re: [PATCH v3 3/3] namei: aggressively check for nd->root escape on ".." resolution |
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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.
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