From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A7D152ED2F; Wed, 23 Sep 2026 14:36:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790174195; cv=none; b=Ic6xDK6TKF0No4GT3G981L4AgaxfgzjqFUIwEAw1UoE+hgfeNggAFHgWFI54oLpo6w/NTub7Ni0lgykfe61CGXjUDRSQ1GRRZP1ysOF9kngowc8NW/Oe3nVS/ldGPLu3K68dbKSp60EIyQncMCFfMaVZY+1NZPPa0vatV7ImHyU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790174195; c=relaxed/simple; bh=UnTANAPOGpVu8H1VWkBKGotZNYFG7juzZ+y+9xfVROc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mzJijn6VyJrugSLAln5SV6Qt2PiTOhYufprYiPE5UD5bvOKBDyQyjYLIfDrSANJ+hf3gpHRd08Uyb+Q3Tp9Fg3NQz8iweoon/TeYCLJYFVsHxSEJwNP45+b7UEGyjXwrgZ+QECg1JLEPpHGw6TQL9dxMS0TLExsIh9CAXcG3CnU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FEz4MFzS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FEz4MFzS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6EE51F000FF; Wed, 23 Sep 2026 14:36:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790174194; bh=psORWQ5fKWrG5jHCzDh1WDDRF+Y1w2Ztki+oeWy/yjc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FEz4MFzSwSSA1uQJqEYfEiyFT925jZmSRba37TDV8uNp1K4bQ9TY+rdkdLm18mD8Z CLlYN8xJ5rJByhCktCMUaxXoGXgVsexFgEMiCye9o0dkP0tVUB2+y3vp6ffDyoqM+1 FvJZ0YswW9EWS6yxayMKmdOzaoEMd6JcdBta3f0I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , Steffen Klassert , Liu Jian , Sasha Levin Subject: [PATCH 6.18 021/398] xfrm: add missing rcu_read_lock(), skb_dst_force() and dev_hold() for xfrm_trans_reinject() Date: Wed, 23 Sep 2026 16:01:35 +0200 Message-ID: <20260923140643.984923166@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140643.441954610@linuxfoundation.org> References: <20260923140643.441954610@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d2f5082f9e84653fa1a9e8aebaaff23e688f5e19 ] syzbot reported a suspicious RCU usage warning in ip6_pkt_drop(): WARNING: suspicious RCU usage in ip6_pkt_drop include/net/addrconf.h:389 suspicious rcu_dereference_check() usage! Call Trace: __in6_dev_get_safely include/net/addrconf.h:389 [inline] ip6_pkt_drop+0x596/0x610 net/ipv6/route.c:4620 ip6_pkt_discard+0x1c/0x30 net/ipv6/route.c:4651 xfrm_trans_reinject+0x324/0x630 net/xfrm/xfrm_input.c:806 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486 When commit 4f4920669d21 ("xfrm: Reinject transport-mode packets through workqueue") converted xfrm_trans_reinject from a tasklet to a workqueue, the reinjection loop ceased running in softirq context. Workqueue workers run in process context where local_bh_disable() does not enter an RCU read-side critical section under CONFIG_PREEMPT_RCU. Because finish callbacks (such as ip6_rcv_finish) expect to run under an RCU read lock (performing route lookups, l3mdev lookups, and accessing RCU-protected data structures), invoking them in workqueue context without rcu_read_lock() triggers RCU lockdep warnings. Furthermore, packets queued to the workqueue via xfrm_trans_queue_net() may carry non-refcounted (noref) dst entries (e.g. from ip_route_input_noref). Additionally, on netdevice unregistration, dst_dev_put() replaces dst->dev with blackhole_netdev, so dst entries do not keep skb->dev alive while queued in the workqueue. Fix these issues by: 1. Calling skb_dst_force(skb) in xfrm_trans_queue_net() while still in the caller's RCU section to ensure dst is reference-counted before queuing. 2. Holding a reference on skb->dev via dev_hold()/dev_put() across workqueue deferral so skb->dev remains valid during finish() callback processing. 3. Acquiring rcu_read_lock() around the finish callback invocation loop in xfrm_trans_reinject(). Fixes: 4f4920669d21 ("xfrm: Reinject transport-mode packets through workqueue") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Steffen Klassert Cc: Liu Jian Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/xfrm/xfrm_input.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c index cfee63a6c87d2..b4c1cee1dbae7 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -794,12 +794,17 @@ static void xfrm_trans_reinject(struct work_struct *work) spin_unlock_bh(&trans->queue_lock); local_bh_disable(); + rcu_read_lock(); while ((skb = __skb_dequeue(&queue))) { struct net *net = XFRM_TRANS_SKB_CB(skb)->net; + struct net_device *dev = skb->dev; XFRM_TRANS_SKB_CB(skb)->finish(net, NULL, skb); + if (dev) + dev_put(dev); put_net(net); } + rcu_read_unlock(); local_bh_enable(); } @@ -815,12 +820,18 @@ int xfrm_trans_queue_net(struct net *net, struct sk_buff *skb, if (skb_queue_len(&trans->queue) >= READ_ONCE(net_hotdata.max_backlog)) return -ENOBUFS; + if (skb_dst(skb) && !skb_dst_force(skb)) + return -EHOSTUNREACH; + BUILD_BUG_ON(sizeof(struct xfrm_trans_cb) > sizeof(skb->cb)); hold_net = maybe_get_net(net); if (!hold_net) return -ENODEV; + if (skb->dev) + dev_hold(skb->dev); + XFRM_TRANS_SKB_CB(skb)->finish = finish; XFRM_TRANS_SKB_CB(skb)->net = hold_net; spin_lock_bh(&trans->queue_lock); -- 2.53.0