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=1793700626; b=ribNw3yfjp/ibjrNXyJFIqm0tGzmQ1JjwSXsay0UgwZnyOW4zQvxMT+KIShd20FFSqCG infCypmWnm3/rpgMNbDaWOSmwAKO5ygC9c/jAd1tK2doQGbEjLUJ5yg96K7q6kZXBDvgU o/6Tc9aPx0tL1Mw+3ogfuZ0JyZpltJCKkmEADFOZG7Gv3sgLOgSSW1UvtlS8bvf8eaNKs vetPTdMfV+bhu2BnQ8FRpKIUaGlEjZNK0WYwPZ8I1v7ou/4ovBxYTCc09Xr8C3/pErStS bXChUG1ykpr4h39lNchA8Qx+BK03B5eDdHy50W2PjVTv22oYpf53SHqxva7MMLbTivQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793700626; h=Received:DKIM-Signature:Subject:To:Cc:From:Date:Message-ID: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=bi7rC5VF8B1FTc9cKBNPDmt4Af9kmyGQSCeR070x2Ok=; b=5b8m232qSmlBT6Xe81u2gApCyAes4Z+6JEvbEduh/RXJsIW/KA/g6t0c4l3W9Pobogko JQWO/lEqn7Bza+qOXJw/c0xUiXKhiEhxjFSLOI9+3drJ/3DdaJyD4+57P2K+cuK7UDbJx bK+GfHJVz5lLe/YM7s5yhq0PNVLPufXpjOi6FZFH2EjpQHaLt+ArCPc4fBWwE9AmsX5n4 7LB+x44f6ro1kstz0cwNrkziADhNc7dXeJ2pUKs6e+kkNsm+UVO8rhruRt2N1NVs+a290 aIQDw3AV9vlVwWt7Y8HyVSCRyQ7pyPzu3Nq7SAGxdzn/EXTwlyylXb6XnylVKQfOTRg== 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=Dm6GtQeH; 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 2902B60A380F for ; Tue, 3 Nov 2026 10:10:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=Dm6GtQeH Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2AC71F0093A; Tue, 3 Nov 2026 10:10:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793700625; bh=bi7rC5VF8B1FTc9cKBNPDmt4Af9kmyGQSCeR070x2Ok=; h=Subject:To:Cc:From:Date; b=Dm6GtQeHuOwpbVNQGe83w0x613QvP2NMY7mCR7xUtYKzJvmRVOzciF86++VFsC0nF tFcs+cWnQ5EuP0Lq/3mFL23GSOFDTTIhid8u7hAK1Wb3b0td0wYtnDiPnH1BB3LILl 9jRCLhHcRnIP5KU/WgaFrqZVs7RFj1NbLI3vTnKM= Subject: FAILED: patch "[PATCH] net/sched: sch_teql: fix use-after-free on lower qdisc drop" failed to apply to 5.15-stable tree To: owen@verialabs.com,horms@kernel.org,jhs@mojatatu.com,pabeni@redhat.com Cc: From: Date: Tue, 03 Nov 2026 11:10:24 +0100 Message-ID: <2026110324-gown-kettle-7dce@gregkh> 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-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 782d6bb8f9b8e9d8591181662222bf74cd3ecf79 # git commit -s git send-email --to '' --in-reply-to '2026110324-gown-kettle-7dce@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 782d6bb8f9b8e9d8591181662222bf74cd3ecf79 Mon Sep 17 00:00:00 2001 From: owen kwan Date: Sat, 24 Oct 2026 10:34:15 -0400 Subject: [PATCH] net/sched: sch_teql: fix use-after-free on lower qdisc drop The issue: teql_master_xmit() tests the slave's ndo_start_xmit() return value against NETDEV_TX_OK alone. A slave that consumes the skb but returns an error code (rc < NET_XMIT_MASK, e.g. NET_XMIT_DROP) is treated as if the skb were still owned, so the loop restores skb->dev and calls __skb_pull() on it. A VLAN slave returns the result of dev_queue_xmit() from its ndo_start_xmit() (propagated since cbbef5e18307), and when the lower qdisc drops the packet that value is NET_XMIT_DROP after the skb has been freed, giving a use-after-free in teql_master_xmit(). The Fix: test for consumption with dev_xmit_complete(), which accepts NETDEV_TX_OK and every rc < NET_XMIT_MASK, matching other callers that need to distinguish consumed results from busy. Only NETDEV_TX_OK keeps the packet counted in tx_packets/tx_bytes and advances the slave; a consumed result that is neither a success nor NET_XMIT_CN ends the attempt and is charged to tx_dropped, so lower-qdisc drops are no longer reported as good transmits. NET_XMIT_CN is counted like success because it can accompany acceptance of the current packet: pfifo_head_drop drops the old head, enqueues the current skb and returns NET_XMIT_CN. Conditions to recreate the bug: With CONFIG_NET_SCH_TEQL, CONFIG_VLAN_8021Q and CONFIG_DUMMY enabled, add lkrdummy0 (dummy) and lkrvlan0 (VLAN id 37 on lkrdummy0); set a pfifo limit 0 root on lkrdummy0 and a teql0 root on lkrvlan0; bring teql0 up with an address and send one UDP packet to it. The VLAN xmit returns NET_XMIT_DROP from the lower qdisc while holding a freed skb. Fixes: 572a9d7b6fc7 ("net: allow to propagate errors through ->ndo_hard_start_xmit()") Link: https://lore.kernel.org/netdev/179248763469.3135.1739559328868319628@kernel.org/ Link: https://lore.kernel.org/netdev/20261023162821.GN708417@horms.kernel.org/ Cc: stable@vger.kernel.org Signed-off-by: owen kwan Signed-off-by: Jamal Hadi Salim Reviewed-by: Simon Horman Link: https://patch.msgid.link/QDISC-Y0BY.v2.r0.20261024060625-2@mojatatu.com Signed-off-by: Paolo Abeni diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c index 6764f0dd38df..70c948a26f80 100644 --- a/net/sched/sch_teql.c +++ b/net/sched/sch_teql.c @@ -360,12 +360,18 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) case 0: if (__netif_tx_trylock(slave_txq)) { unsigned int length = qdisc_pkt_len(skb); + int rc = NETDEV_TX_BUSY; skb->dev = slave; - if (!netif_xmit_frozen_or_stopped(slave_txq) && - netdev_start_xmit(skb, slave, slave_txq, false) == - NETDEV_TX_OK) { - __netif_tx_unlock(slave_txq); + if (!netif_xmit_frozen_or_stopped(slave_txq)) + rc = netdev_start_xmit(skb, slave, slave_txq, false); + __netif_tx_unlock(slave_txq); + if (dev_xmit_complete(rc)) { + if (rc != NETDEV_TX_OK && rc != NET_XMIT_CN) { + master->tx_dropped++; + rcu_read_unlock(); + return NETDEV_TX_OK; + } raw_spin_lock_irqsave(&master->slaves_lock, flags); if (rcu_dereference_protected(master->slaves, lockdep_is_held(&master->slaves_lock)) == q) @@ -379,7 +385,6 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) rcu_read_unlock(); return NETDEV_TX_OK; } - __netif_tx_unlock(slave_txq); } if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0))) busy = 1;