Hello Paul, On Thu, Sep 11, 2025 at 12:45:21PM -0700, Paul Eggert wrote: > Yes, I've been thinking of doing something more straightforward instead: > > When extracting a file named A/B/C/D, make sure that A, A/B, and A/B/C all > fall under the target directory (this is the current directory by default; > or it can the directory established by -C). Similarly for A/B/C/D in the > non-default case where D is not unlinked before re-creating it. > > The obvious implementation of this is slow because it's redoing namei in > user space. However, I know how to make it almost as as fast as tar is now, > at least on GNU/Linux; just haven't gotten around to implementing it yet.
Thanks for considering it. Would it work to use realpath(3)? One could just check whether the realpath of A/B/C has the realpath of . as its prefix. (I suppose though that using realpath(3) is equivalent to redoing namei in user space.) Regards, Pavel
