On Fri, 16 Sept 2022 at 08:13, NeilBrown <neilb@xxxxxxx> wrote: > @@ -4554,44 +4590,83 @@ int do_linkat(int olddfd, struct filename *old, int newdfd, > if (flags & AT_SYMLINK_FOLLOW) > how |= LOOKUP_FOLLOW; > retry: > - error = filename_lookup(olddfd, old, how, &old_path, NULL); > + err2 = 0; > + error = filename_parentat(olddfd, old, how, &old_path, > + &old_last, &old_type); > if (error) > goto out_putnames; > + error = -EISDIR; > + if (old_type != LAST_NORM && !(flags & AT_EMPTY_PATH)) > + goto out_putnames; > + error = filename_parentat(newdfd, new, (how & LOOKUP_REVAL), &new_path, > + &new_last, &new_type); > + if (error) > + goto out_putoldpath; > > - new_dentry = filename_create(newdfd, new, &new_path, > - (how & LOOKUP_REVAL)); > - error = PTR_ERR(new_dentry); > - if (IS_ERR(new_dentry)) > - goto out_putpath; > + err2 = mnt_want_write(new_path.mnt); > > error = -EXDEV; > if (old_path.mnt != new_path.mnt) > - goto out_dput; > + goto out_putnewpath; > + lock_link(new_path.dentry, old_path.dentry, flags); > + > + new_dentry = __lookup_hash(&new_last, new_path.dentry, how & LOOKUP_REVAL); > + error = PTR_ERR(new_dentry); > + if (IS_ERR(new_dentry)) > + goto out_unlock; > + error = -EEXIST; > + if (d_is_positive(new_dentry)) > + goto out_dput_new; > + if (new_type != LAST_NORM) > + goto out_dput_new; > + > + error = err2; > + if (error) > + goto out_dput_new; > + > + if (flags & AT_EMPTY_PATH) > + old_dentry = dget(old_path.dentry); > + else > + old_dentry = __lookup_hash(&old_last, old_path.dentry, how); This will break AT_SYMLINK_FOLLOW. And yes, we can add all the lookup logic to do_linkat() at which point it will about 10x more complex than it was. Thanks, Miklos
