From nobody Tue Sep 16 00:28:58 2025 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 9CD83C54EBD for ; Mon, 9 Jan 2023 16:39:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235163AbjAIQjj (ORCPT ); Mon, 9 Jan 2023 11:39:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234470AbjAIQja (ORCPT ); Mon, 9 Jan 2023 11:39:30 -0500 Received: from mail-il1-x12a.google.com (mail-il1-x12a.google.com [IPv6:2607:f8b0:4864:20::12a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8691F34D67 for ; Mon, 9 Jan 2023 08:39:28 -0800 (PST) Received: by mail-il1-x12a.google.com with SMTP id h26so5084443ila.11 for ; Mon, 09 Jan 2023 08:39:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=Xrg136BCp0PmT+E9WTU4STUIwjfV5DcN5FDK70FqYcI=; b=aIFfWS0cT4UCU3f6+rKm+5rHYgjr2Tnu5w/qCdXoxWFfN6ueukXs1tp/iAqvpFruK7 6tN75Q/bqrlviXjadh9+tAa31LXc9OPq9r3CqA566MBQTvoURfX3gKuDU8AqrQDRBhyZ c06SMvz82ThLUp5ehRVxJiZtnjJqPdFRKpKEA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Xrg136BCp0PmT+E9WTU4STUIwjfV5DcN5FDK70FqYcI=; b=JAK58c7xrXxFX6nB52hKckYRnk8p29E3t+P28iDKRifAMw57O/eMbKHFIRadfkdyYu JUgE1NbVOjWjJpkyi9mT6AuxLrqwAmkwxNrAPHxvlT1mqtgDJkGsLhfxDFH3mVKS+Yxb V9ZQyuWYTuj6aAkDupdg315K6Yk2S2smI0WMRmssNVew0uMF9FsRO/3TEg2cIaaH9EJp RXSNYy4DFqY5VqcZBpbnLRyA0BhF0w7Lyb6CL/zlFx8iw2XMx/9tteiAqfwDcGk8I7uQ 25TkaXE1f5e5urwHYP4Btg1ZtnQtiH3gIE4iUKuq4airkQrTgxhFVuD0uP8xX/PXF/98 VpLw== X-Gm-Message-State: AFqh2kpals7aZwH2kB6SE2DP8Xvz7Z4uNQ4Fnb1theflOZeFHI5bJhKV IvOEM9qpJwWQSsVyy8Py6R00mg== X-Google-Smtp-Source: AMrXdXsKno4G65HN0v8xsEuZOmhCnZC8InIBvJDkqhetZl7+YX9yYEGFPoFLGieuDFZqVW7UzXp4lQ== X-Received: by 2002:a05:6e02:2205:b0:30d:92c4:8d6 with SMTP id j5-20020a056e02220500b0030d92c408d6mr9444298ilf.10.1673282367876; Mon, 09 Jan 2023 08:39:27 -0800 (PST) Received: from localhost.localdomain ([70.57.89.124]) by smtp.gmail.com with ESMTPSA id w17-20020a92ad11000000b0030c44ed932asm2790684ilh.29.2023.01.09.08.39.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Jan 2023 08:39:27 -0800 (PST) From: Frederick Lawler To: jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, kuba@kernel.org, linux-kernel@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, zymon.heidrich@gmail.com, phil@nwl.cc, netdev@vger.kernel.org, kernel-team@cloudflare.com, Frederick Lawler , stable@vger.kernel.org, Jakub Sitnicki Subject: [PATCH net] net: sched: disallow noqueue for qdisc classes Date: Mon, 9 Jan 2023 10:39:06 -0600 Message-Id: <20230109163906.706000-1-fred@cloudflare.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" While experimenting with applying noqueue to a classful queue discipline, we discovered a NULL pointer dereference in the __dev_queue_xmit() path that generates a kernel OOPS: # dev=3Denp0s5 # tc qdisc replace dev $dev root handle 1: htb default 1 # tc class add dev $dev parent 1: classid 1:1 htb rate 10mbit # tc qdisc add dev $dev parent 1:1 handle 10: noqueue # ping -I $dev -w 1 -c 1 1.1.1.1 [ 2.172856] BUG: kernel NULL pointer dereference, address: 0000000000000= 000 [ 2.173217] #PF: supervisor instruction fetch in kernel mode ... [ 2.178451] Call Trace: [ 2.178577] [ 2.178686] htb_enqueue+0x1c8/0x370 [ 2.178880] dev_qdisc_enqueue+0x15/0x90 [ 2.179093] __dev_queue_xmit+0x798/0xd00 [ 2.179305] ? _raw_write_lock_bh+0xe/0x30 [ 2.179522] ? __local_bh_enable_ip+0x32/0x70 [ 2.179759] ? ___neigh_create+0x610/0x840 [ 2.179968] ? eth_header+0x21/0xc0 [ 2.180144] ip_finish_output2+0x15e/0x4f0 [ 2.180348] ? dst_output+0x30/0x30 [ 2.180525] ip_push_pending_frames+0x9d/0xb0 [ 2.180739] raw_sendmsg+0x601/0xcb0 [ 2.180916] ? _raw_spin_trylock+0xe/0x50 [ 2.181112] ? _raw_spin_unlock_irqrestore+0x16/0x30 [ 2.181354] ? get_page_from_freelist+0xcd6/0xdf0 [ 2.181594] ? sock_sendmsg+0x56/0x60 [ 2.181781] sock_sendmsg+0x56/0x60 [ 2.181958] __sys_sendto+0xf7/0x160 [ 2.182139] ? handle_mm_fault+0x6e/0x1d0 [ 2.182366] ? do_user_addr_fault+0x1e1/0x660 [ 2.182627] __x64_sys_sendto+0x1b/0x30 [ 2.182881] do_syscall_64+0x38/0x90 [ 2.183085] entry_SYSCALL_64_after_hwframe+0x63/0xcd ... [ 2.187402] Previously in commit d66d6c3152e8 ("net: sched: register noqueue qdisc"), NULL was set for the noqueue discipline on noqueue init so that __dev_queue_xmit() falls through for the noqueue case. This also sets a bypass of the enqueue NULL check in the register_qdisc() function for the struct noqueue_disc_ops. Classful queue disciplines make it past the NULL check in __dev_queue_xmit() because the discipline is set to htb (in this case), and then in the call to __dev_xmit_skb(), it calls into htb_enqueue() which grabs a leaf node for a class and then calls qdisc_enqueue() by passing in a queue discipline which assumes ->enqueue() is not set to NULL. Fix this by not allowing classes to be assigned to the noqueue discipline. Linux TC Notes states that classes cannot be set to the noqueue discipline. [1] Let's enforce that here. Links: 1. https://linux-tc-notes.sourceforge.net/tc/doc/sch_noqueue.txt Fixes: d66d6c3152e8 ("net: sched: register noqueue qdisc") Cc: stable@vger.kernel.org Signed-off-by: Frederick Lawler Reviewed-by: Jakub Sitnicki --- net/sched/sch_api.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 2317db02c764..72d2c204d5f3 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1133,6 +1133,11 @@ static int qdisc_graft(struct net_device *dev, struc= t Qdisc *parent, return -ENOENT; } =20 + if (new && new->ops =3D=3D &noqueue_qdisc_ops) { + NL_SET_ERR_MSG(extack, "Cannot assign noqueue to a class"); + return -EINVAL; + } + err =3D cops->graft(parent, cl, new, &old, extack); if (err) return err; --=20 2.34.1