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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74E38C388F9 for ; Sat, 31 Oct 2020 11:44:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C9AC20739 for ; Sat, 31 Oct 2020 11:44:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604144691; bh=vfy2sWIyXsStIzgal4RoOaUGPPRHIy+IWfKZyaltyRQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=oQzqAvQsy90CAqqKazT+xhyK5s7eJ2mj8dC23sQCgcfj1BI8ZzU6tyF1dyM198Tfk oTs04w8yblkykPeFhh1j7qbD3w++b8rIak9U1uYrHb/MlkraIPWdHBKOBbGpdRKNaB CDeGY/WxvTtnl2ESCJ2mmkeT5n894VOJE07NP+k8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728205AbgJaLou (ORCPT ); Sat, 31 Oct 2020 07:44:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:45200 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728196AbgJaLoo (ORCPT ); Sat, 31 Oct 2020 07:44:44 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 32D8D2074F; Sat, 31 Oct 2020 11:44:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604144683; bh=vfy2sWIyXsStIzgal4RoOaUGPPRHIy+IWfKZyaltyRQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=E8rrA2TO0kVMN9wgMKVkCJsuFgB4SYdEMTe2jmvPYDkpghErqttJlVyb7AcZwLHI/ ho/icpo31mplcBmJ7JY+SveFixR++Gd0ZH4GakCC84nMyorx4XLe9Ew3I8r4Xi3YwY 6kAJ/WN0xJXb/m6J1tsEMKRQb0Hg0CW/NFy5Rb7Q= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Aleksandr Nogikh , syzbot+ec762a6342ad0d3c0d8f@syzkaller.appspotmail.com, Stephen Hemminger , Jakub Kicinski Subject: [PATCH 5.9 41/74] netem: fix zero division in tabledist Date: Sat, 31 Oct 2020 12:36:23 +0100 Message-Id: <20201031113502.012204025@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201031113500.031279088@linuxfoundation.org> References: <20201031113500.031279088@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: Aleksandr Nogikh [ Upstream commit eadd1befdd778a1eca57fad058782bd22b4db804 ] Currently it is possible to craft a special netlink RTM_NEWQDISC command that can result in jitter being equal to 0x80000000. It is enough to set the 32 bit jitter to 0x02000000 (it will later be multiplied by 2^6) or just set the 64 bit jitter via TCA_NETEM_JITTER64. This causes an overflow during the generation of uniformly distributed numbers in tabledist(), which in turn leads to division by zero (sigma != 0, but sigma * 2 is 0). The related fragment of code needs 32-bit division - see commit 9b0ed89 ("netem: remove unnecessary 64 bit modulus"), so switching to 64 bit is not an option. Fix the issue by keeping the value of jitter within the range that can be adequately handled by tabledist() - [0;INT_MAX]. As negative std deviation makes no sense, take the absolute value of the passed value and cap it at INT_MAX. Inside tabledist(), switch to unsigned 32 bit arithmetic in order to prevent overflows. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Aleksandr Nogikh Reported-by: syzbot+ec762a6342ad0d3c0d8f@syzkaller.appspotmail.com Acked-by: Stephen Hemminger Link: https://lore.kernel.org/r/20201028170731.1383332-1-aleksandrnogikh@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_netem.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -330,7 +330,7 @@ static s64 tabledist(s64 mu, s32 sigma, /* default uniform distribution */ if (dist == NULL) - return ((rnd % (2 * sigma)) + mu) - sigma; + return ((rnd % (2 * (u32)sigma)) + mu) - sigma; t = dist->table[rnd % dist->size]; x = (sigma % NETEM_DIST_SCALE) * t; @@ -812,6 +812,10 @@ static void get_slot(struct netem_sched_ q->slot_config.max_packets = INT_MAX; if (q->slot_config.max_bytes == 0) q->slot_config.max_bytes = INT_MAX; + + /* capping dist_jitter to the range acceptable by tabledist() */ + q->slot_config.dist_jitter = min_t(__s64, INT_MAX, abs(q->slot_config.dist_jitter)); + q->slot.packets_left = q->slot_config.max_packets; q->slot.bytes_left = q->slot_config.max_bytes; if (q->slot_config.min_delay | q->slot_config.max_delay | @@ -1037,6 +1041,9 @@ static int netem_change(struct Qdisc *sc if (tb[TCA_NETEM_SLOT]) get_slot(q, tb[TCA_NETEM_SLOT]); + /* capping jitter to the range acceptable by tabledist() */ + q->jitter = min_t(s64, abs(q->jitter), INT_MAX); + return ret; get_table_failure: