From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50502 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388557AbeHDLMr (ORCPT ); Sat, 4 Aug 2018 07:12:47 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, kernel test robot , Dmitry Safonov , "David S. Miller" Subject: [PATCH 4.4 107/124] netlink: Dont shift with UB on nlk->ngroups Date: Sat, 4 Aug 2018 11:01:36 +0200 Message-Id: <20180804082706.463051350@linuxfoundation.org> In-Reply-To: <20180804082702.434482435@linuxfoundation.org> References: <20180804082702.434482435@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Safonov [ Upstream commit 61f4b23769f0cc72ae62c9a81cf08f0397d40da8 ] On i386 nlk->ngroups might be 32 or 0. Which leads to UB, resulting in hang during boot. Check for 0 ngroups and use (unsigned long long) as a type to shift. Fixes: 7acf9d4237c4 ("netlink: Do not subscribe to non-existent groups"). Reported-by: kernel test robot Signed-off-by: Dmitry Safonov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/netlink/af_netlink.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -983,7 +983,11 @@ static int netlink_bind(struct socket *s if (err) return err; } - groups &= (1UL << nlk->ngroups) - 1; + + if (nlk->ngroups == 0) + groups = 0; + else + groups &= (1ULL << nlk->ngroups) - 1; bound = nlk->bound; if (bound) {