Re: [PATCH 3/8][RFC v05] NFSv3: add client implementation of XATTR protocol

["Serge E. Hallyn" <serge@hallyn.com>]

Quoting James Morris (jmorris@namei.org):
...
> +int nfs3_proc_getxattr(struct inode *inode, const char *namespace,
> +		       const char *name, void *value, size_t size)
> +{
...
> +	res.xattr_val_len = size;
> +	res.xattr_val = kmalloc(size, GFP_KERNEL);
> +	if (!res.xattr_val)
> +		return -ENOMEM;
> +
> +	dprintk("NFS call getxattr %s%s %zd\n", namespace, name, size);
> +
> +	msg.rpc_proc = &server->client_xattr->cl_procinfo[XATTRPROC3_GETXATTR];
> +	nfs_fattr_init(&fattr);
> +	status = rpc_call_sync(server->client_xattr, &msg, 0);
> +
> +	dprintk("NFS reply getxattr: status=%d len=%d\n",
> +		status, res.xattr_val_len);
> +
> +	switch (status) {
> +	case 0:
> +		status = nfs_refresh_inode(inode, &fattr);
> +		break;
> +	case -EPFNOSUPPORT:
> +	case -EPROTONOSUPPORT:
> +		dprintk("NFS_V3_XATTR extension not supported; disabling\n");
> +		server->caps &= ~NFS_CAP_XATTR;
> +	case -ENOTSUPP:
> +		status = -EOPNOTSUPP;
> +	default:
> +		goto cleanup;
> +	}
> +
> +	status = res.xattr_val_len;
> +	if (status <= size)

res.xattr_val_len was set to size, as was status, and none of the
3 has been changed, so here status can't be > size can it?

Was this just a safety to prevent overrun, or did you mean to
do some other check?  (If a safety, then you'll still return
status > size, but with garbage in value, so i think you'd want
to also change status)

> +		memcpy(value, res.xattr_val, status);