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=1793831318; b=vL34uq90lFixKhe7yhyC9XbIE+667bwrjIUEUctq7SWNC3kHzZKD0NapAJ/FPUPB3EUw TXFPohbTRo0qoSOTgUjrwOL+vmLmx5oSc2eoy8HIsrLBAfqVsBmqpyPf/kkAXbvc19cCd yMdQesEL+YnIsdgr/rYGw4iFxuJL9etqWVQQVFXB0HR3naVIQDgTaHHHk+L2zlUwVHkX6 3NrVyfceMrqPESFpjaZ8+NG1XwDlgf+MAzDRBVC8VSKIhl8qZ4MDIWskRTYl9P4H47Tuq LHCe00eYJyZX5ym2UpFA71iCndd5ZlwCAAD4190bmPr52BqDMdxJD0DNfUrdOkdxPRA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831318; 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=X0Cr/riFZplm9+XxIR1eIbELkrTzbxH7w7PRCU3rk+M=; b=LHFg1DqREi+tsm51NtHg212G1CMcmkTRN9K61/vIFlnSLmSRT8OXUiykY9IkR80M3n04 bfM5DG5H4sxO5R5lDFiYAsIYwahaO+ucCsoJelx2WSY1M1P6c6PDca67firXPWSwgHV7j C5S5YjGDxz/38JugGVgcw0Z0cLdp3XpzoBxeeGhrBqKu4rx9aLc6timc6ZW6F17GrQeGX Rd2I2vn9w/EfxyG58zRifjvS1irOaaQEakEFGhdQd8BiD+04vpBmoump8Is0u1gC43WDA QmkoQOFLU2g54WD8SP8ONlpX3cWfJwSl9whrrhpEaExWk52EDYnZMIzvuKh0WXltuTw== 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=e2LxgzX7; 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 1A8B8606EE9E; Wed, 4 Nov 2026 22:28:38 +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=e2LxgzX7 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A87291F00A02; Wed, 4 Nov 2026 22:28:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831318; bh=X0Cr/riFZplm9+XxIR1eIbELkrTzbxH7w7PRCU3rk+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=e2LxgzX7x5+BrCHl1es9CaOLDbbX4DLe6wglUZx4ykAnHVZ73mdJxc7H26sX4UNUY n9B5XhTzn4LHJnRGR0cnG+HoBdJ4vSoQQcyvL134hz+4Lnen7wXkddEbo9TJ0q41RE SGtS8A0Ji6K2lpfsTz5wpXmOLZ5xm3drCHL0p40A= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, owen kwan , Jamal Hadi Salim , Simon Horman , Paolo Abeni Subject: [PATCH 6.18 0629/1005] net/sched: sch_teql: fix use-after-free on lower qdisc drop Date: Wed, 4 Nov 2026 16:06:02 -0500 Message-ID: <20261104211101.411849417@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: owen kwan commit 782d6bb8f9b8e9d8591181662222bf74cd3ecf79 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_teql.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) --- a/net/sched/sch_teql.c +++ b/net/sched/sch_teql.c @@ -347,12 +347,18 @@ restart: 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) @@ -366,7 +372,6 @@ restart: rcu_read_unlock(); return NETDEV_TX_OK; } - __netif_tx_unlock(slave_txq); } if (netif_xmit_stopped(netdev_get_tx_queue(dev, 0))) busy = 1;