From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794591264; b=unUqcl1azfjXWrRzhGbExNtVkrqTNx9sCRmGalV8XVKeimiurwtMy3k7vCk9oBpCDMP/ l94E9Cskr9SRD2Jzz+inx6sqfmVUdiuAJtfAt+OOc/YWo3I077w0RxhtOCMug9RdU+Fdk dTtLw5GR0qFkZNpyRk7s7Q8xEvWwh2asjZEV5nc/bwGatWLb+skw8wknCNE0yWb4d7PUC uTQHIsl1cyzRJrguL3/oPQ14KGrh2DQBE2YkVwtPjL4oE6CBBfo4zqo2UhwNis7ZzMIAG oylWN02KIDSmB861cEnrqW0/38jVbP2f/BTvquYIEIo/k/wEniStw+MSPTbCgAs1aPA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591264; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=DAuhBssBilgPRC9d5bEbganJdqLk4xe3NLHZilg2SWw=; b=hYMSP6JeZyvlmbDg14i1FqRh7vlqpiXrHKIz2lVB5Xpb7KWrggSLvRxI6xNaji9A5dez gq9tQNKK2vg2LpM04bVdL8+EPC5Es3ogxgHGGN5slkEzb1lhjz75S07NRckpgJaXF70zI mPZkRLmyKuaJrVYv5/3mNTejUOJ437pczSC3tKtfSrh8lZUJR37R6EIH/9FccskC6l8g5 lbmwZpgrq1cMOJ1g8gberQXrc+w5tDf8h81kCNU/k932Zl5BBzJqlDLR526+NWsfk4p3W 4GvdYyYxDaETsaEGk0CzRLzIRJded5gSm+5eT2ynOgdmg/DVZal4Frzcd5oZQclJE2g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qMbemFq3; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 39A0C6076F9B; Fri, 13 Nov 2026 17:34:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qMbemFq3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id D98071F000C4; Fri, 13 Nov 2026 17:34:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591264; bh=DAuhBssBilgPRC9d5bEbganJdqLk4xe3NLHZilg2SWw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qMbemFq3AKL4QvZlItJuKm02MvpB8SneyZHoumEl3Ro0oRPmmJYgnIKiTG7f/diWA krBt66gOWD4EpjGWpRUo3zTHflrCRMyHoQHCcTPDrvLerr0s43QkGCDwP9X56fi0lh R+qNh9R9oHp5KEl1jdo0wW/Qc8+50Fa++s0WnIjg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Sashiko (nipa)" , Jamal Hadi Salim , Simon Horman , Paolo Abeni , Sasha Levin Subject: [PATCH 6.12 335/670] net/sched: clamp skb->queue_mapping before indexing the tx queue Date: Fri, 13 Nov 2026 10:48:19 -0500 Message-ID: <20261113153823.215562298@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jamal Hadi Salim [ Upstream commit f19f2b308beb158d0e6f6eb806ced636e4ebf6ce ] This issue was caught by Sashiko (nipa). A producer-side path cap is already merged (ea4d4b5dddb5); this patch adds the matching consumer-side caps. The issue: The tx queue is picked and capped in netdev_core_pick_tx() before the __dev_xmit_skb() qdisc enqueue path. A tc BPF program running inside an egress qdisc (not clsact) can then change __sk_buff->queue_mapping; that store is never re-checked. bpf_convert_ctx_access() bounds it only by NO_QUEUE_MAPPING, not by the device's queue count. Two consumers read the stale value: - On dequeue, qdisc_restart() calls netdev_get_tx_queue(), which indexes dev->_tx[]. netdev_get_tx_queue() guards it with just a DEBUG_NET_WARN_ON_ONCE, so sch_direct_xmit() takes the out-of-bounds txq->_xmit_lock and writes txq->xmit_lock_owner past the end of the allocation on non-lltx devices such as ifb. Drivers that index their rings from skb_get_queue_mapping() (ex: ifb) go out of range the same way. - On enqueue, taprio_enqueue() indexes q->qdiscs[] with the same value; the array is sized dev->num_tx_queues. A duplicating netem on a child qdisc clones the skb and re-enqueues the clone at the taprio root (qdisc_root_bh()) through a direct rootq->enqueue() call, so the value reaches taprio_enqueue() before any dequeue cap runs. The Fix: Cap the mapping at the consumers and write the capped value back, so the qdisc's _tx[] lookup, the taprio q->qdiscs[] lookup and any later driver read stay in range. On the dequeue side the cap folds into the dequeue path instead of a separate walk over the returned list: dequeue_skb() caps the head, and each bulk helper caps the element it appends. For a qdisc that is not TCQ_F_ONETXQUEUE, netdev_cap_txqueue() logs a ratelimited notice and selects queue 0. A TCQ_F_ONETXQUEUE qdisc is bound to a single tx queue: dequeue_skb() uses q->dev_queue for the frozen check, the BQL limit and the trace point, while qdisc_restart() transmits on the skb's queue. Capping an out-of-range mapping to queue 0 would therefore send a per-queue child's skb through a different queue than the one it was dequeued for. On mq, mqprio, taprio and htb offload children, a stopped queue 0 could then park the list in q->gso_skb, and the later wake would schedule queue 0's own child instead of this qdisc. Pin a TCQ_F_ONETXQUEUE mapping to the qdisc's own queue to keep the documented invariant. The pin covers every mapping, not only an out-of-range one: an in-range mapping that a filter sets on one of those per-queue children is rewritten to the child's own queue, and this path does not call netdev_cap_txqueue(), so it logs no notice. On a single-queue device qdisc_create() sets TCQ_F_ONETXQUEUE, so the one-queue trigger described below also takes this branch and is corrected without a notice. That also keeps a bulk list on one queue by construction: every element of a TCQ_F_ONETXQUEUE qdisc, including a follower changed by a filter, is pinned to q->dev_queue before it is appended. The fast bulk helper therefore needs no head comparison and no skb_bad_txq requeue; the slow helper, used only by non-ONETXQUEUE qdiscs, still compares and requeues a mismatched follower, where a wake on any queue reschedules q. On the enqueue side taprio_enqueue() caps the mapping against real_num_tx_queues and writes it back before selecting q->qdiscs[queue], so a duplicating child cannot steer the clone out of the array. Conditions to recreate the bug: The dequeue path: load a SCHED_CLS or SCHED_ACT program that stores __sk_buff->queue_mapping (a tc BPF action is enough), attach it to a transmit qdisc (for example a matchall filter on a prio root), and send a packet. With a 1-queue device a store of 1 indexes one past dev->_tx[]. Under KASAN with panic_on_warn=1 the unfixed kernel faults with "BUG: KASAN: slab-out-of-bounds in sch_direct_xmit". Loading the program needs CAP_BPF/CAP_SYS_ADMIN, so the trigger is root. The enqueue path: on a multi-queue device, install a software taprio root, graft a prio child with a duplicating netem on every class, and store an out-of-range queue_mapping from a matchall+bpf filter on the prio. The duplicate is re-enqueued at the taprio root and indexes q->qdiscs[] past dev->num_tx_queues; the unfixed kernel faults in taprio_enqueue_one(). Same CAP_BPF/CAP_SYS_ADMIN requirement. Fixes: 74e31ca850c1 ("bpf: add skb->queue_mapping write access from tc clsact") Reported-by: Sashiko (nipa) Closes: https://lore.kernel.org/netdev/179033713973.2160803.4914570693994398206@kernel.org/ Link: https://lore.kernel.org/netdev/179329777513.3134.12135506558709584471@kernel.org/ Link: https://lore.kernel.org/netdev/179293123940.3134.1149128679923234677@kernel.org/ Link: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/QDISC-MD1X.v4.r0.20261021042722-1%40mojatatu.com Link: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/QDISC-MD1X.v3.r0.20261015165943-1%40mojatatu.com Link: https://netdev-ai.bots.linux.dev/sashiko/#/patchset/QDISC-MD1X.v1.20261005193231%40mojatatu.com Link: https://lore.kernel.org/netdev/20261015125822.GH83879@horms.kernel.org/ Cc: stable@vger.kernel.org Signed-off-by: Jamal Hadi Salim Reviewed-by: Simon Horman Link: https://patch.msgid.link/QDISC-MD1X.v6.r0.20261029162633-1@mojatatu.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- net/sched/sch_generic.c | 41 ++++++++++++++++++++++++++++++++++++----- net/sched/sch_taprio.c | 5 +++++ 2 files changed, 41 insertions(+), 5 deletions(-) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index b8619b306fca2..e5b65ea313c85 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -70,9 +70,34 @@ static void qdisc_maybe_clear_missed(struct Qdisc *q, #define SKB_XOFF_MAGIC ((struct sk_buff *)1UL) +/* Re-cap a stale queue_mapping; an ONETXQUEUE qdisc pins q->dev_queue. */ +static u16 qdisc_cap_skb_tx_queue(struct Qdisc *q, struct sk_buff *skb) +{ + u16 queue = skb_get_queue_mapping(skb); + struct net_device *dev = qdisc_dev(q); + u16 capped; + + if (q->flags & TCQ_F_ONETXQUEUE) + capped = q->dev_queue - netdev_get_tx_queue(dev, 0); + else + capped = netdev_cap_txqueue(dev, queue); + + if (unlikely(capped != queue)) + skb_set_queue_mapping(skb, capped); + + return capped; +} + +static struct netdev_queue *skb_cap_tx_queue(struct Qdisc *q, + struct sk_buff *skb) +{ + return netdev_get_tx_queue(qdisc_dev(q), + qdisc_cap_skb_tx_queue(q, skb)); +} + static inline struct sk_buff *__skb_dequeue_bad_txq(struct Qdisc *q) { - const struct netdev_queue *txq = q->dev_queue; + const struct netdev_queue *txq; spinlock_t *lock = NULL; struct sk_buff *skb; @@ -84,7 +109,8 @@ static inline struct sk_buff *__skb_dequeue_bad_txq(struct Qdisc *q) skb = skb_peek(&q->skb_bad_txq); if (skb) { /* check the reason of requeuing without tx lock first */ - txq = skb_get_tx_queue(txq->dev, skb); + /* re-cap: real_num_tx_queues may have shrunk */ + txq = skb_cap_tx_queue(q, skb); if (!netif_xmit_frozen_or_stopped(txq)) { skb = __skb_dequeue(&q->skb_bad_txq); if (qdisc_is_percpu_stats(q)) { @@ -198,6 +224,8 @@ static void try_bulk_dequeue_skb(struct Qdisc *q, if (!nskb) break; + /* Every element of an ONETXQUEUE qdisc is pinned to q->dev_queue. */ + qdisc_cap_skb_tx_queue(q, nskb); bytelimit -= nskb->len; /* covers GSO len */ skb->next = nskb; skb = nskb; @@ -215,7 +243,6 @@ static void try_bulk_dequeue_skb_slow(struct Qdisc *q, struct sk_buff *skb, int *packets) { - int mapping = skb_get_queue_mapping(skb); struct sk_buff *nskb; int cnt = 0; @@ -223,7 +250,9 @@ static void try_bulk_dequeue_skb_slow(struct Qdisc *q, nskb = q->dequeue(q); if (!nskb) break; - if (unlikely(skb_get_queue_mapping(nskb) != mapping)) { + /* A tc BPF store may have changed the mapping; cap it. */ + if (unlikely(qdisc_cap_skb_tx_queue(q, nskb) != + skb_get_queue_mapping(skb))) { qdisc_enqueue_skb_bad_txq(q, nskb); break; } @@ -268,7 +297,7 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate, if (xfrm_offload(skb)) *validate = true; /* check the reason of requeuing without tx lock first */ - txq = skb_get_tx_queue(txq->dev, skb); + txq = skb_cap_tx_queue(q, skb); if (!netif_xmit_frozen_or_stopped(txq)) { skb = __skb_dequeue(&q->gso_skb); if (qdisc_is_percpu_stats(q)) { @@ -304,6 +333,8 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate, skb = q->dequeue(q); if (skb) { bulk: + /* cap the head; the bulk helpers cap every appended element */ + qdisc_cap_skb_tx_queue(q, skb); if (qdisc_may_bulk(q)) try_bulk_dequeue_skb(q, skb, txq, packets, budget); else diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 5091ffc3f4754..54d0136dfe6c5 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -631,6 +631,11 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch, int queue; queue = skb_get_queue_mapping(skb); + if (unlikely(queue >= qdisc_dev(sch)->real_num_tx_queues)) { + /* A tc BPF program may have stored an out-of-range mapping. */ + queue = netdev_cap_txqueue(qdisc_dev(sch), queue); + skb_set_queue_mapping(skb, queue); + } child = q->qdiscs[queue]; if (unlikely(child == &noop_qdisc)) -- 2.53.0