Re: [PATCH v3 7/9] vfs: move open right after ->tmpfile()

[Al Viro <viro@zeniv.linux.org.uk>]

On Wed, Sep 21, 2022 at 05:06:57AM +0200, Miklos Szeredi wrote:
> On Tue, 20 Sept 2022 at 22:57, Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Tue, Sep 20, 2022 at 09:36:30PM +0200, Miklos Szeredi wrote:
> >
> > >       inode = child->d_inode;
> >
> > Better
> >         inode = file_inode(file);
> >
> > so that child would be completely ignored after dput().
> >
> > > +     error = vfs_tmpfile(mnt_userns, &path, file, op->mode);
> > > +     if (error)
> > >               goto out2;
> > > -     dput(path.dentry);
> > > -     path.dentry = child;
> > > -     audit_inode(nd->name, child, 0);
> > > +     audit_inode(nd->name, file->f_path.dentry, 0);
> > >       /* Don't check for other permissions, the inode was just created */
> > > -     error = may_open(mnt_userns, &path, 0, op->open_flag);
> >
> > Umm...  I'm not sure that losing it is the right thing - it might
> > be argued that ->permission(..., MAY_OPEN) is to be ignored for
> > tmpfile (and the only thing checking for MAY_OPEN is nfs, which is
> > *not* going to grow tmpfile any time soon - certainly not with these
> > calling conventions), but you are also dropping the call of
> > security_inode_permission(inode, MAY_OPEN) and that's a change
> > compared to what LSM crowd used to get...
> 
> Not losing it, just moving it into vfs_tmpfile().

Sorry, missed that bit...