On Fri, Dec 02, 2016 at 10:57:42AM +0100, Miklos Szeredi wrote: > On Tue, Oct 11, 2016 at 2:50 PM, Andreas Gruenbacher > <agruenba@xxxxxxxxxx> wrote: > > Normally, deleting a file requires MAY_WRITE access to the parent > > directory. With richacls, a file may be deleted with MAY_DELETE_CHILD access > > to the parent directory or with MAY_DELETE_SELF access to the file. > > > > To support that, pass the MAY_DELETE_CHILD mask flag to inode_permission() > > when checking for delete access inside a directory, and MAY_DELETE_SELF > > when checking for delete access to a file itself. > > > > The MAY_DELETE_SELF permission overrides the sticky directory check. > > And MAY_DELETE_SELF seems totally inappropriate to any kind of rename, > since from the point of view of the inode we are not doing anything at > all. The modifications are all in the parent(s), and that's where the > permission checks need to be. I'm having a hard time finding an authoritative reference here (Samba people might be able to help), but my understanding is that Windows gives this a meaning something like "may I delete a link to this file". (And not even "may I delete the *last* link to this file", which might also sound more logical.) --b. > > > @@ -2780,14 +2780,20 @@ static int may_delete_or_replace(struct inode *dir, struct dentry *victim, > > BUG_ON(victim->d_parent->d_inode != dir); > > audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); > > > > - error = inode_permission(dir, mask); > > + error = inode_permission(dir, mask | MAY_WRITE | MAY_DELETE_CHILD); > > + if (!error && check_sticky(dir, inode)) > > + error = -EPERM; > > + if (error && IS_RICHACL(inode) && > > + inode_permission(inode, MAY_DELETE_SELF) == 0 && > > + inode_permission(dir, mask) == 0) > > + error = 0; > > Why is MAY_WRITE missing here? Everything not aware of > MAY_DELETE_SELF (e.g. LSMs) will still need MAY_WRITE otherwise this > is going to be a loophole. > > Thanks, > Miklos > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
