From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:50772 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730488AbeKLFsZ (ORCPT ); Mon, 12 Nov 2018 00:48:25 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "kernel test robot" , "David S. Miller" , "Dmitry Safonov" Date: Sun, 11 Nov 2018 19:49:05 +0000 Message-ID: Subject: [PATCH 3.16 305/366] netlink: Don't shift with UB on nlk->ngroups In-Reply-To: Sender: stable-owner@vger.kernel.org List-ID: 3.16.61-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Safonov commit 61f4b23769f0cc72ae62c9a81cf08f0397d40da8 upstream. 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: Ben Hutchings --- 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 @@ -927,7 +927,11 @@ 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; if (nlk->portid) if (nladdr->nl_pid != nlk->portid)