Casey Schaufler <ca...@schaufler-ca.com> wrote:
> > + * @inode_copy_up:
> > + * Generate the secid associated with the destination inode when a unioned
>
> NAK.
>
> You can't just deal with the access label, nor can you assume that there
> is exactly one. Don't use secids. ...
Okay, I've changed the documentation to:
* @inode_copy_up:
* Appropriately label the destination inode when a unioned file is copied
* up from a lower layer to the union/overlay layer.
* @src indicates the file that is being copied up.
* @dst indicates the file that has being created by the copy up.
* Returns 0 on success or a negative error code on error.
> > + * @inode_copy_up_xattr:
> > + * Filter/modify the xattrs being copied up when a unioned file is copied
> > + * up from a lower layer to the union/overlay layer.
> > + * @src indicates the file that is being copied up.
> > + * @dst indicates the file that has being created by the copy up.
> > + * @name indicates the name of the xattr.
> > + * @value, *@size indicate the payload of the xattr.
> > + * Returns 0 to accept the xattr, 1 to discard the xattr or a negative
> > + * error code to abort the copy up. The xattr buffer must be at least
> > + * XATTR_SIZE_MAX in capacity and the contents may be modified and *@size
> > + * changed appropriately.
>
> Who is going to call this?
Anyone that copies up a file from the lower layer in a union to an upper
layer. Overlayfs for example. Unionmount for another.
> How are is the caller going to know all the xattr names that matter?
The caller has no idea. That's why it presents them all here.
> > +static int cap_inode_copy_up_xattr(struct dentry *src, struct dentry *dst,
> > + const char *name, void *value, size_t *size)
> > +{
> > + return 0;
> > +}
> > +
>
> Does this mean that without LSM help no xattrs ever get copied?
No. This is merely a filter. The caller reads the xattr, presents them to
this hook and then, if not asked to discard, writes the xattr. I've added a
bit to the end of the comment to this effect.
David
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