From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 1632437D11F for ; Wed, 8 Jul 2026 06:06:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783490806; cv=none; b=WLZmWF5SEmw1jst6db6OqSs18xJwVF2NJE8W5TUElrfUtcQb/quzvYkRP2AnWXeRjA6R3qjJ2dWzA8q5DI6ZDlaCFHFkZ9vuKmp3WyxO7YmJSTW5v4SdEvSWMVZIcia7jSN23iwNuAcYQpRhcvqAtCoMyQyDn19JqHYlCLFf9m8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783490806; c=relaxed/simple; bh=cJAKCsATZu1hv6z4ZbiF7Btxv6VeiniLdNRhSY8UXCQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ndoxlwKV9ukp/2QSxMd526/JXqyKUYWXGwVREmLadYDqLqBAFOfdU9Ghcn29EzbNBE8I28NkTqQNuykvNWDLNRKsuD9KCg73W+ScY5dk+ZVf7IKTy9JNYz7/hwmjafhN5qmIEB3zSuhkHFWeuWu7XtvI7AU6WEcyntIhIK9amJk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=jojbmrBi; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="jojbmrBi" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783490802; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wCj9Nnj2Mldbj02SmTcTXwvZVO75xuL0hZ3WqcMIS0M=; b=jojbmrBiVYDRlWy6EYAO/pY6uH0o0estbGyedKzSDvIJi3UvWSoYrheT/ogzoKWWbrXvPy qhw8VFN4QsCMIDh9vv9UomROQjh6iJxBcI40J/yVgmu9KmjQG2R9Ku2EFaSY9CPFyuzGZ1 TKroHwwYeD7+CKgyPi9ePMq3lKLSJDI= From: xuanqiang.luo@linux.dev To: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern , Ido Schimmel Cc: Simon Horman , Kuniyuki Iwashima , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Xuanqiang Luo Subject: [PATCH net-next v3 2/2] ipv4: snapshot dst.dev in ip_rt_send_redirect() and ip_rt_get_source() Date: Wed, 8 Jul 2026 14:05:37 +0800 Message-ID: <20260708060537.17188-3-xuanqiang.luo@linux.dev> In-Reply-To: <20260708060537.17188-1-xuanqiang.luo@linux.dev> References: <20260708060537.17188-1-xuanqiang.luo@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Xuanqiang Luo rt_flush_dev() can replace rt->dst.dev with blackhole_netdev while RCU readers are running. ip_rt_send_redirect() and ip_rt_get_source() both read rt->dst.dev more than once and use the results in one operation. If rt->dst.dev changes between those reads, the operation can use values from two devices. For example, ip_rt_send_redirect() can use in_dev from the old device and the L3 master ifindex from blackhole_netdev. Read rt->dst.dev once in these two functions and use the snapshot for the later device accesses. Signed-off-by: Xuanqiang Luo --- net/ipv4/route.c | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index b668375df71e2..4fed07cae7da2 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -874,21 +874,23 @@ void ip_rt_send_redirect(struct sk_buff *skb) { struct rtable *rt = skb_rtable(skb); struct in_device *in_dev; + struct net_device *dev; struct inet_peer *peer; - struct net *net; int log_martians; + struct net *net; int vif; rcu_read_lock(); - in_dev = __in_dev_get_rcu(rt->dst.dev); + dev = dst_dev_rcu(&rt->dst); + in_dev = __in_dev_get_rcu(dev); if (!in_dev || !IN_DEV_TX_REDIRECTS(in_dev)) { rcu_read_unlock(); return; } log_martians = IN_DEV_LOG_MARTIANS(in_dev); - vif = l3mdev_master_ifindex_rcu(rt->dst.dev); + vif = l3mdev_master_ifindex_rcu(dev); - net = dev_net(rt->dst.dev); + net = dev_net_rcu(dev); peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr, vif); if (!peer) { rcu_read_unlock(); @@ -1287,29 +1289,32 @@ void ip_rt_get_source(u8 *addr, struct sk_buff *skb, struct rtable *rt) { __be32 src; - if (rt_is_output_route(rt)) + rcu_read_lock(); + if (rt_is_output_route(rt)) { src = ip_hdr(skb)->saddr; - else { - struct fib_result res; + } else { + struct net_device *dev = dst_dev_rcu(&rt->dst); + struct net *net = dev_net_rcu(dev); struct iphdr *iph = ip_hdr(skb); + struct fib_result res; struct flowi4 fl4 = { .daddr = iph->daddr, .saddr = iph->saddr, .flowi4_dscp = ip4h_dscp(iph), - .flowi4_oif = rt->dst.dev->ifindex, + .flowi4_oif = dev->ifindex, .flowi4_iif = skb->dev->ifindex, .flowi4_mark = skb->mark, }; - rcu_read_lock(); - if (fib_lookup(dev_net(rt->dst.dev), &fl4, &res, 0) == 0) - src = fib_result_prefsrc(dev_net(rt->dst.dev), &res); + if (fib_lookup(net, &fl4, &res, 0) == 0) + src = fib_result_prefsrc(net, &res); else - src = inet_select_addr(rt->dst.dev, + src = inet_select_addr(dev, rt_nexthop(rt, iph->daddr), RT_SCOPE_UNIVERSE); - rcu_read_unlock(); } + rcu_read_unlock(); + memcpy(addr, &src, 4); } -- 2.43.0