Re: [PATCH v2 01/18] vfs: add miscattr ops

From: Al Viro
Date: Wed Mar 24 2021 - 08:29:37 EST


On Wed, Mar 24, 2021 at 09:45:02AM +0100, Miklos Szeredi wrote:
> On Wed, Mar 24, 2021 at 6:03 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Mon, Mar 22, 2021 at 03:48:59PM +0100, Miklos Szeredi wrote:
> >
> > minor nit: copy_fsxattr_{to,from}_user() might be better.
> >
> > > +int fsxattr_copy_to_user(const struct miscattr *ma, struct fsxattr __user *ufa)
> > > +{
> > > + struct fsxattr fa = {
> > > + .fsx_xflags = ma->fsx_xflags,
> > > + .fsx_extsize = ma->fsx_extsize,
> > > + .fsx_nextents = ma->fsx_nextents,
> > > + .fsx_projid = ma->fsx_projid,
> > > + .fsx_cowextsize = ma->fsx_cowextsize,
> > > + };
> >
> > That wants a comment along the lines of "guaranteed to be gap-free",
> > since otherwise you'd need memset() to avoid an infoleak.
>
> Isn't structure initialization supposed to zero everything not
> explicitly initialized?

All fields, but not the padding...

> The one in io_uring() seems wrong also, as a beast needing
> file_dentry() should never get out of overlayfs and into io_uring:

That one would be wrong in overlayfs as well - we'd better had the
same names in all layers...

> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -9297,7 +9297,7 @@ static void __io_uring_show_fdinfo(struct
> io_ring_ctx *ctx, struct seq_file *m)
> struct file *f = *io_fixed_file_slot(ctx->file_data, i);
>
> if (f)
> - seq_printf(m, "%5u: %s\n", i, file_dentry(f)->d_iname);
> + seq_printf(m, "%5u: %pD\n", i, f);
> else
> seq_printf(m, "%5u: <none>\n", i);
> }
>
>
> Thanks,
> Miklos