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SubjectRe: [PATCH v2 01/18] vfs: add miscattr ops
On Wed, Mar 24, 2021 at 6:03 AM Al Viro <viro@zeniv.linux.org.uk> 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?

>
> > +static int ioctl_getflags(struct file *file, void __user *argp)
> > +{
> > + struct miscattr ma = { .flags_valid = true }; /* hint only */
> > + unsigned int flags;
> > + int err;
> > +
> > + err = vfs_miscattr_get(file_dentry(file), &ma);
>
> Umm... Just to clarify - do we plan to have that ever called via
> ovl_real_ioctl()? IOW, is file_dentry() anything other than a way
> to spell ->f_path.dentry here?

Indeed, file_dentry() only makes sense when called from a layer inside
overlayfs.

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

--- 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

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