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 54EF14A2605 for ; Tue, 1 Sep 2026 19:28:40 +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=1788290921; cv=none; b=YRZMYzKJBhZA8HzOKxi65j/n6SI3vCEZ0Odex9JuUqpeSWG/sKIZ/7DJd+6EnLxEDYP7RwoO7lFXK8m3N/xitShdHqXAEhn/ZVLi8QK5jvKqPWGxuPuUi0buXY711KzDnUelUX0Lh/55tUioeJooM5vhX3zMgHjvzC/Sqrs3LGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788290921; c=relaxed/simple; bh=k221c6neLI8uvxOri7VgoI20n6IN8bEUWdN3zZO62gk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=l9eA/HrU9tMpzbxlHAR+I31aqTF6yT+a6uNsUBA4sFf0oISyml4sPqFRRmB12ter+8UdCZBSSDJSBHJQwZrLmxXb04qcwlbLSTcQo1k2hnqBD9lsCCG9I+nNXejdsBJ03zILafIONkrok9cEKfa/UDywDG1HT/iVzhdyicD9m7U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=izjACg2Y; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="izjACg2Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83DB01F00A3D; Tue, 1 Sep 2026 19:28:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788290920; bh=l5degComSAAB1ABHmuv2A3GiFRIDXhg76XKCWIqbXS0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=izjACg2Y583KKVyE0pPzhLvLYrP0NbcQ14b3awkAx+/XbC7mRZg/njFP38XnSX3Rk GGIP4NKsK4O6QD2TJ5W0L40pteLoedz/raXRfQcV8LR6ec81jkzny61ZYsKeE1gvSc W2P2TuPXNCtwJkhuJbi+r8MmBVbz022Fu4yp/TVw8AzPQLjeYx0hvDP3aQDX76kmg0 TXm976ceZrvyA0kHt2cP3gLeBD6F+QjxiTDhC17KQSa0pznrWBZKFqkTq+Xwbd0bV7 AOxT2vn+NzlorrhDAf3PJ2TY4IyCR1zFq8KhGFcM0XK0Rbw0wsnXT6vOV/M3UIH2e4 Ek6q7lTzP3aAQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Eric Dumazet , David Ahern , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1.y 1/4] net: dst: introduce dst->dev_rcu Date: Tue, 1 Sep 2026 15:28:35 -0400 Message-ID: <20260901192838.1439895-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026083117-magnitude-talisman-5d78@gregkh> References: <2026083117-magnitude-talisman-5d78@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit caedcc5b6df1b2e2b5f39079e3369c1d4d5c5f50 ] Followup of commit 88fe14253e18 ("net: dst: add four helpers to annotate data-races around dst->dev"). We want to gradually add explicit RCU protection to dst->dev, including lockdep support. Add an union to alias dst->dev_rcu and dst->dev. Add dst_dev_net_rcu() helper. Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://patch.msgid.link/20250828195823.3958522-2-edumazet@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: 2640e6419594 ("net: advertise TCP MSS from the configured MTU, not the learned PMTU") Signed-off-by: Sasha Levin --- include/net/dst.h | 11 +++++++---- include/net/ip6_route.h | 2 ++ net/core/dst.c | 2 +- net/ipv4/route.c | 4 ++-- net/ipv6/route.c | 5 ++--- 5 files changed, 14 insertions(+), 10 deletions(-) diff --git a/include/net/dst.h b/include/net/dst.h index 20a76e532afbb..d149ffa0948c0 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -23,7 +23,10 @@ struct sk_buff; struct dst_entry { - struct net_device *dev; + union { + struct net_device *dev; + struct net_device __rcu *dev_rcu; + }; struct dst_ops *ops; unsigned long _metrics; unsigned long expires; @@ -557,11 +560,11 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu) static inline struct net_device *dst_dev_rcu(const struct dst_entry *dst) { - /* In the future, use rcu_dereference(dst->dev) */ - WARN_ON_ONCE(!rcu_read_lock_held()); - return READ_ONCE(dst->dev); + return rcu_dereference(dst->dev_rcu); } +#define dst_dev_net_rcu(dst) dev_net_rcu(dst_dev_rcu(dst)) + static inline struct net_device *skb_dst_dev_rcu(const struct sk_buff *skb) { return dst_dev_rcu(skb_dst(skb)); diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h index 7c0184c09392f..ca67b63ae8866 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -270,6 +270,8 @@ static inline bool ipv6_anycast_destination(const struct dst_entry *dst, int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, int (*output)(struct net *, struct sock *, struct sk_buff *)); +#define dst6_mtu(dst) dst_mtu(dst) + static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb) { const struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ? diff --git a/net/core/dst.c b/net/core/dst.c index 8db87258d1450..c6cd97cd7dd3f 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -151,7 +151,7 @@ void dst_dev_put(struct dst_entry *dst) dst->ops->ifdown(dst, dev, true); dst->input = dst_discard; dst->output = dst_discard_out; - dst->dev = blackhole_netdev; + rcu_assign_pointer(dst->dev_rcu, blackhole_netdev); netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker, GFP_ATOMIC); } diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 783460ebfc471..0fd2d07dbc144 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1069,7 +1069,7 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu) return; rcu_read_lock(); - net = dev_net_rcu(dst->dev); + net = dst_dev_net_rcu(dst); if (mtu < net->ipv4.ip_rt_min_pmtu) { lock = true; mtu = min(old_mtu, net->ipv4.ip_rt_min_pmtu); @@ -1367,7 +1367,7 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst) struct net *net; rcu_read_lock(); - net = dev_net_rcu(dst->dev); + net = dst_dev_net_rcu(dst); advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size, net->ipv4.ip_rt_min_advmss); rcu_read_unlock(); diff --git a/net/ipv6/route.c b/net/ipv6/route.c index e198a5eb24c64..1f02a13481f1e 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -3226,15 +3226,14 @@ EXPORT_SYMBOL_GPL(ip6_sk_redirect); static unsigned int ip6_default_advmss(const struct dst_entry *dst) { - struct net_device *dev = dst->dev; - unsigned int mtu = dst_mtu(dst); + unsigned int mtu = dst6_mtu(dst); struct net *net; mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr); rcu_read_lock(); - net = dev_net_rcu(dev); + net = dst_dev_net_rcu(dst); if (mtu < net->ipv6.sysctl.ip6_rt_min_advmss) mtu = net->ipv6.sysctl.ip6_rt_min_advmss; -- 2.53.0