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=1793713414; b=uF0VV8kNAHq/M9fMgSN8P6UMPk1pQkg2rGLd6SgqovNau403F6wqODNLZy2RD/8mKJdf Z0gAQp5P7xM1zay4g3oj+KmX+cGKsFm3swCnJAejqyCJQlFFjSMhTGRPb4raRol0wHiVQ hGmIO9hB/z+bgMaFB6iPAOxF3K3Tcjs+aPXAHamw13I3nrqfJtEfTBNUy5J2Z0tjIO6F9 7bI9Mt8wWwzfZDoTNr/kq9UQWvFuHKFy5+tbgdvAe0BrPLXQJpzQl9wz85py8WQpuZxlJ QSQsLesCSQdhqadJrWlKjv6j5VdANpZzt+5j2wh2xtqqXCizGx/XjwGkX/XOvxncvFw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793713414; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=yZfIsC58hDG5nePhG/0L8WYWzy8KpUJsSEBr8PzIokQ=; b=Hs8E1g+E+omyuUwqxb1si0L4QbjhnpJ1HkJQ/WMJA6zH4nG/8pwvi7b7Le6lMa4OGJWw H/MVNGY8zrGkH6VILji6ztwNG44LInbiKJCmWvKk87EKJwNLpsTveBwKGRoMlNFSt9Hxi 5jt+MMyd06EXBfBLSWMom4MlvZbbVlOBrzl1zplDP6Hhir872psfSBPrM0Ph1PiTd8Sag EwB0C4WW6L4/QBv2PrPvGtwfxGrorC17gQ5Cjtu9k5qfze9yKuOaXS8Z1oQjknB6EExR5 S+3qB2AIObCFxWzImLRF+jIGnCVqJo7Ews1kM6qBtq34pOZgjq9i53DXC1hTB5aPEBQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NjZh6GFg; 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 0E912606D804 for ; Tue, 3 Nov 2026 13:43:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NjZh6GFg Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10B8E1F00919; Tue, 3 Nov 2026 13:43:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793713413; bh=yZfIsC58hDG5nePhG/0L8WYWzy8KpUJsSEBr8PzIokQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NjZh6GFgycLrO/rAyaJdt1Mc29mCSnWBp5SBQBpo0HVvabDeYK6kg5TnFi1pRmoM6 64JLyYeS9rB41IfmME3z06xgj04KIJ5AZ4GOjfD3CU6GZi/ybEP89hN00ZmpimGftx ZOHtr/Ow3tFxA7uttWqMWExE2LPD6aBUb2R72T/kQ/SP97UGnm+J3sdyNCHwkpez4h qvWhUxBuA0vH4m+RrcmjwMC+aoNd7We8VmvCZKZbH4dhG2snGknWSFimY0BSfYptmR 2xBEab47xWzhp43uLaiFVMW8KuLJlSGWLZuMjGGG2tZ5avJIXPFph5xSmAGwBs2b5K MGkUiDBe+FVDg== From: Sasha Levin To: stable@vger.kernel.org Cc: owen kwan , Jamal Hadi Salim , Simon Horman , Paolo Abeni , Sasha Levin Subject: [PATCH 5.15.y] net/sched: sch_teql: fix use-after-free on lower qdisc drop Date: Tue, 3 Nov 2026 08:43:31 -0500 Message-ID: <20261103134300.3967501-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110324-gown-kettle-7dce@gregkh> References: <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-Transfer-Encoding: 8bit From: owen kwan [ Upstream commit 782d6bb8f9b8e9d8591181662222bf74cd3ecf79 ] 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 [ sashal: Omitted rcu_read_unlock() because teql_master_xmit() has no corresponding RCU read lock. ] Signed-off-by: Sasha Levin --- net/sched/sch_teql.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c index 00ac4386627c7..9057d4f2ee5c6 100644 --- a/net/sched/sch_teql.c +++ b/net/sched/sch_teql.c @@ -311,19 +311,23 @@ 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++; + return NETDEV_TX_OK; + } master->slaves = NEXT_SLAVE(q); netif_wake_queue(dev); master->tx_packets++; master->tx_bytes += length; return NETDEV_TX_OK; } - __netif_tx_unlock(slave_txq); } if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0))) busy = 1; -- 2.53.0