From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f173.google.com (mail-pf1-f173.google.com [209.85.210.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F380533F38A for ; Fri, 10 Apr 2026 15:40:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775835645; cv=none; b=KBnQ5pnJwKCdja8voNSGNHU6VH944+3ospx2e7MFIQo79pTYVfgJryfjkHftNhC6e74gqp/oRRvNE9rAQV9wo3syL9A7uhS1O6F+PVY7pxy9um9nlMuZewWdt+h7E0eFetryknNR2REwlVQi3pM/wG3YhUNEpVCMK3U1hxga2/Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775835645; c=relaxed/simple; bh=WD2kItpaljpKgAUiK0BAZZLxKk2fz6dofRlZDFLW91k=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=HVCj7oXk/Qh0uNtvAPkUVAzniwnhWEiBhslOzs/1XoAAvC1xucGaaxQGCF4ovSc7g4UamrMHeKJjiq02gAEwxPMEdUbBHgL3O4Q2ogwFkJ8aAR5w+VWR9LCeEUf1aa22KRVhjtELMMUKTXiXu6XGX32XiMLW7RnS/Li9C2bSrag= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=FzlL0uh+; arc=none smtp.client-ip=209.85.210.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="FzlL0uh+" Received: by mail-pf1-f173.google.com with SMTP id d2e1a72fcca58-82418b0178cso1181534b3a.1 for ; Fri, 10 Apr 2026 08:40:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1775835643; x=1776440443; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=swiKP2dfJ7x8QYcvk/9GMzyobZM35ErBhsi1fgDGHl8=; b=FzlL0uh+QG8PbEEfWZCpzqaG2uY2TaAhpqBYKI+LqfJ0CrW3caowuDB8f7vumeqtm1 OXTgQ4iHWaUfm/DI8q5QMN32Oqc8PNU9E+Iv/0DqujAHLqpQLmdHSZ7cpvQ6GD8Gz5BM KMpvN/25w5G7a+0Fd078YlpXnyLHeEP8cB9yNjXCOPEbHbwY1rWsSN6SL7bKPvB9oLDC D3h5Fxj2w7EbUzBcFV/GEoZsnIUw6TEfJv4rJHzREI0AGyLV8ts6UL4rHTawcGrjGhID DDZmrSYltc7ZaYU3D1alpaOIrm9Bi18P4g53LUIMngGOmZf6cL5Z4YRX4LJ2krDbV4wv phaw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775835643; x=1776440443; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=swiKP2dfJ7x8QYcvk/9GMzyobZM35ErBhsi1fgDGHl8=; b=rgfDZ5wnYJfxeDVrY6pc9sHMIYx67sVSkmlIla5tvMFOu3S3Qc58vYeeua+TOo6u4y rXUGBPrk0XsuDfVft2bkzRJ23Md8Za4W1ukdfKXLJ1TcVXhB4yKCxYqGr+zDDplCFOyQ 7cZF9nJVmhB9+jH/NQxtH6H6o5Hp2fOIMzIhw0BmDvemDZz4khD8LkL3QaF6l9L3e659 BIChjKYdZ8JXS537RfEPdqglesYoJbU0MpW+IGaBOyNx1i4zo2DKIgYwtcn4QGvw2DVo U5XzNxYsaYkjiQRsc+HYfPtTJj78xqqSVVqR2qxgE33QAvI4hopsP+iCJt1rOIxte0Bu 4y5g== X-Forwarded-Encrypted: i=1; AJvYcCWh+H7CWE2XLbL/O5IKMTW6xoHNxL3sTCN4uTTchyP4GfpbFiMZi6uEy7cTY6qp1FcFnSobwHU=@vger.kernel.org X-Gm-Message-State: AOJu0Yx/qEKjwLUDBKBV5PFX0uWe1jjJeP8bIuIN8KYoYKSq5B1Aun5V 7qmtloSvtkikVTaFIc4fEXFI80s0rfrxAUz3Sh9BszcR3hPk5HuSP4jS X-Gm-Gg: AeBDietMqw+71OYMkH/lmxLVX4p5HV824oPVa8j0/y3Ouoj76fBi7LEl9cLmMqK9XE3 O5O8QNo08b/1rJ69GjvhSlzopDPh0enLcUiEkX6WGq/01bXtUf9ph69HGREfRw7EQOahKgjl26r wQyFkvx8GKufa9FdORfW2pTrvCKLAz5kBWpVULfxvZy/hyFha2m4Wj2Ha1CQ4NE/K5r2FHwxNe7 zF7YMCugXniznpGYF7YCwZHLfX47Lr2vUoZ68ZasqIylX8hOhjL9Q8Vd7msLUCPIfKQTGSkhCjN U/4qFbQPI9hOTcmLugnFqXCDdAO1M/knGxKD1TIAvavNcjk/wc3wDIXn/+H6cunCYF42OwH7uFu Y0QqrhnG8imazQP0LzOuWXd/zjfjI+z3owXxD+MYiB1orWD12raOvOw+Pj4ZrDpzYAHUrQ8XpCP uVKvx8N8iXWm5ydUnX6dfHk90EjAOgEDSiIBmw/0bHMPwr575R5/SZUR2z4lXq9bFZ5BjyAO1ZV TipURp/NPOk X-Received: by 2002:a05:6a20:2588:b0:39e:f994:f698 with SMTP id adf61e73a8af0-39fe403e6demr4394929637.48.1775835643205; Fri, 10 Apr 2026 08:40:43 -0700 (PDT) Received: from SLSGDTSWING002.tail0ac356.ts.net ([129.126.109.177]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c7921a3e6d2sm2678599a12.32.2026.04.10.08.40.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Apr 2026 08:40:42 -0700 (PDT) From: Weiming Shi To: Vinicius Costa Gomes , Jamal Hadi Salim , Jiri Pirko , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Vladimir Oltean , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH net v2] net/sched: taprio: fix NULL pointer dereference in class dump Date: Fri, 10 Apr 2026 23:39:03 +0800 Message-ID: <20260410153902.955227-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft() is called with new == NULL and stores NULL into q->qdiscs[cl - 1]. Subsequent RTM_GETTCLASS dump operations walk all classes via taprio_walk() and call taprio_dump_class(), which calls taprio_leaf() returning the NULL pointer, then dereferences it to read child->handle, causing a kernel NULL pointer dereference. The bug is reachable with namespace-scoped CAP_NET_ADMIN on any kernel with CONFIG_NET_SCH_TAPRIO enabled. On systems with unprivileged user namespaces enabled, an unprivileged local user can trigger a kernel panic by creating a taprio qdisc inside a new network namespace, grafting an explicit child qdisc, deleting it, and requesting a class dump. The RTM_GETTCLASS dump itself requires no capability. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:taprio_dump_class (net/sched/sch_taprio.c:2475) Call Trace: tc_fill_tclass (net/sched/sch_api.c:1966) qdisc_class_dump (net/sched/sch_api.c:2329) taprio_walk (net/sched/sch_taprio.c:2510) tc_dump_tclass_qdisc (net/sched/sch_api.c:2353) tc_dump_tclass_root (net/sched/sch_api.c:2370) tc_dump_tclass (net/sched/sch_api.c:2431) rtnl_dumpit (net/core/rtnetlink.c:6827) netlink_dump (net/netlink/af_netlink.c:2325) rtnetlink_rcv_msg (net/core/rtnetlink.c:6927) netlink_rcv_skb (net/netlink/af_netlink.c:2550) Fix this by substituting &noop_qdisc when new is NULL in taprio_graft(), following the same pattern used by multiq_graft() and prio_graft(). This ensures q->qdiscs[] slots are never NULL, making control-plane dump paths safe without requiring individual NULL checks. Also update the data-plane NULL guards in taprio_enqueue() and taprio_dequeue_from_txq() to check for &noop_qdisc, so that packets are still dropped cleanly without inflating qlen/backlog counters. Fixes: 665338b2a7a0 ("net/sched: taprio: dump class stats for the actual q->qdiscs[]") Reported-by: Xiang Mei Signed-off-by: Weiming Shi --- v2: - Update NULL checks in taprio_enqueue() and taprio_dequeue_from_txq() to test for &noop_qdisc instead of NULL, preventing qlen/backlog counter inflation when noop_qdisc drops packets (Sashiko) --- net/sched/sch_taprio.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index f721c03514f60..XXXXXXXXX 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -634,7 +634,7 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch, child = q->qdiscs[queue]; - if (unlikely(!child)) + if (unlikely(child == &noop_qdisc)) return qdisc_drop(skb, sch, to_free); if (taprio_skb_exceeds_queue_max_sdu(sch, skb)) { @@ -717,7 +717,7 @@ static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq, int prio; int len; u8 tc; - if (unlikely(!child)) + if (unlikely(child == &noop_qdisc)) return NULL; if (TXTIME_ASSIST_IS_ENABLED(q->flags)) @@ -2183,6 +2183,9 @@ static int taprio_graft(struct Qdisc *sch, unsigned long cl, if (!dev_queue) return -EINVAL; + if (!new) + new = &noop_qdisc; + if (dev->flags & IFF_UP) dev_deactivate(dev); @@ -2196,14 +2199,14 @@ static int taprio_graft(struct Qdisc *sch, unsigned long cl, *old = q->qdiscs[cl - 1]; if (FULL_OFFLOAD_IS_ENABLED(q->flags)) { WARN_ON_ONCE(dev_graft_qdisc(dev_queue, new) != *old); - if (new) + if (new != &noop_qdisc) qdisc_refcount_inc(new); if (*old) qdisc_put(*old); } q->qdiscs[cl - 1] = new; - if (new) + if (new != &noop_qdisc) new->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT; if (dev->flags & IFF_UP) -- 2.43.0