From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F445C433FE for ; Tue, 5 Apr 2022 12:53:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353767AbiDEMtw (ORCPT ); Tue, 5 Apr 2022 08:49:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244530AbiDEJKD (ORCPT ); Tue, 5 Apr 2022 05:10:03 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7923125EBB; Tue, 5 Apr 2022 01:59:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B26E3B81A22; Tue, 5 Apr 2022 08:59:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28815C385A0; Tue, 5 Apr 2022 08:59:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649149182; bh=da01Yu1VRcc/0ZM/zmhrzof8NG1WHBs1WVz1sV/nRo4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=meRpfhKkskr0noF+WQ6ltGty2TRg/ZvmUkvPs5urNMIA8jOxu26RRrGy84l2Tnuj0 Gk1w0D+57pgfgVBNk4cSBo9yCC87zeh4WaN/eQXimrD+tx7472vK8YQ5MuRY1KEaKe PxSPiV5SXuYerCriJU3n9Ww3idJ8EZFmSGWLd63o= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Petr Machata , Ido Schimmel , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.16 0623/1017] af_netlink: Fix shift out of bounds in group mask calculation Date: Tue, 5 Apr 2022 09:25:36 +0200 Message-Id: <20220405070412.775282745@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070354.155796697@linuxfoundation.org> References: <20220405070354.155796697@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Petr Machata [ Upstream commit 0caf6d9922192dd1afa8dc2131abfb4df1443b9f ] When a netlink message is received, netlink_recvmsg() fills in the address of the sender. One of the fields is the 32-bit bitfield nl_groups, which carries the multicast group on which the message was received. The least significant bit corresponds to group 1, and therefore the highest group that the field can represent is 32. Above that, the UB sanitizer flags the out-of-bounds shift attempts. Which bits end up being set in such case is implementation defined, but it's either going to be a wrong non-zero value, or zero, which is at least not misleading. Make the latter choice deterministic by always setting to 0 for higher-numbered multicast groups. To get information about membership in groups >= 32, userspace is expected to use nl_pktinfo control messages[0], which are enabled by NETLINK_PKTINFO socket option. [0] https://lwn.net/Articles/147608/ The way to trigger this issue is e.g. through monitoring the BRVLAN group: # bridge monitor vlan & # ip link add name br type bridge Which produces the following citation: UBSAN: shift-out-of-bounds in net/netlink/af_netlink.c:162:19 shift exponent 32 is too large for 32-bit type 'int' Fixes: f7fa9b10edbb ("[NETLINK]: Support dynamic number of multicast groups per netlink family") Signed-off-by: Petr Machata Reviewed-by: Ido Schimmel Link: https://lore.kernel.org/r/2bef6aabf201d1fc16cca139a744700cff9dcb04.1647527635.git.petrm@nvidia.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/netlink/af_netlink.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 9eba2e648385..6fbc3ea735e5 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -157,6 +157,8 @@ EXPORT_SYMBOL(do_trace_netlink_extack); static inline u32 netlink_group_mask(u32 group) { + if (group > 32) + return 0; return group ? 1 << (group - 1) : 0; } -- 2.34.1