On Mon, Aug 04, 2025 at 04:52:29PM +0100, Al Viro wrote: > On Mon, Aug 04, 2025 at 02:33:13PM +0200, Christian Brauner wrote: > > > + guard(spinlock)(&files->file_lock); > > err = expand_files(files, fd); > > if (unlikely(err < 0)) > > - goto out_unlock; > > - return do_dup2(files, file, fd, flags); > > + return err; > > + err = do_dup2(files, file, fd, flags); > > + if (err < 0) > > + return err; > > > > -out_unlock: > > - spin_unlock(&files->file_lock); > > - return err; > > + return 0; > > } > > NAK. This is broken - do_dup2() drops ->file_lock. And that's why I Right, I missed that. Just say it's broken. You don't need to throw around NAKs pointlessly. It's pretty clear when to drop ptaches without throwing the meat cleaver through the room. > loathe the guard() - it's too easy to get confused *and* assume that The calling conventions of do_dup2() are terrible. The only reason it drops file_lock itself instead of leaving it to the two callers that have to acquire it anyway is because it wants to call filp_close() if there's already a file on that fd. And really the side-effect of dropping a lock implicitly is nasty especially when the function doesn't even indicate that it does that in it's name. And guards are great.
