cifs: Fix use-after-free in SMB2_read

There is a KASAN use-after-free:
BUG: KASAN: use-after-free in SMB2_read+0x1136/0x1190
Read of size 8 at addr ffff8880b4e45e50 by task ln/1009

Should not release the 'req' because it will use in the trace.

Fixes: eccb4422cf97 ("smb3: Add ftrace tracepoints for improved SMB3 debugging")

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org> 4.18+
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
SMB2_select_sec(struct cifs_ses *ses, struct SMB2_sess_data *sess_data)
{
	int type;

	type = smb2_select_sectype(ses->server, ses->sectype);
	cifs_dbg(FYI, "sess setup type %d\n", type);
	if (type == Unspecified) {
		cifs_dbg(VFS,
			"Unable to select appropriate authentication method!");
		return -EINVAL;
	}

	switch (type) {
	case Kerberos:
		sess_data->func = SMB2_auth_kerberos;
		break;
	case RawNTLMSSP:
		sess_data->func = SMB2_sess_auth_rawntlmssp_negotiate;
		break;
	default:
		cifs_dbg(VFS, "secType %d not supported!\n", type);
		return -EOPNOTSUPP;
	}

	return 0;
}

SMB2_select_sec(struct cifs_ses *ses, struct SMB2_sess_data *sess_data)
{
	int type;

	type = smb2_select_sectype(ses->server, ses->sectype);
	cifs_dbg(FYI, "sess setup type %d\n", type);
	if (type == Unspecified) {
		cifs_dbg(VFS,
			"Unable to select appropriate authentication method!");
		return -EINVAL;
	}

	switch (type) {
	case Kerberos:
		sess_data->func = SMB2_auth_kerberos;
		break;
	case RawNTLMSSP:
		sess_data->func = SMB2_sess_auth_rawntlmssp_negotiate;
		break;
	default:
		cifs_dbg(VFS, "secType %d not supported!\n", type);
		return -EOPNOTSUPP;
	}

	return 0;
}
