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 87FBA4DEC1B; Wed, 30 Sep 2026 16:24:36 +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=1790785483; cv=none; b=h2wHHk5cIH2uBCLRdhSNP97LMW0NJyhxobdoquGivNfZIeABrCvCHpNzClylW/v08ezAouf1038TBuJ0mUYefcVBxF1Q1h3RRDejAPDg+A/YrT4ut06pr+KALwaoDX5JvUZT4jqHE8b8/XbXQESWEhxWxKCPU9K03dzH0kTfo8k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790785483; c=relaxed/simple; bh=tANrSEKbsUMsaN28ugbBFUxoeoDOwD8+oOrKIE/4HFg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Nw+n4K0D07aatDJkIM09BJuB2SX5pxDpU7Nz6a+CC/frawFuoq1iYRVtZTEznZwqpoczQbj6/nOYDtC6ctzL/5BhwDxe5aLhe2BZXQjOtZyn0ZEQyd7Tps6i5ZFaq0VKMOwKy9c6IzEiuY7kjl8qmqVC9xhneVDhNdSES4mlfHk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=S47hz5pH; 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="S47hz5pH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8AB581F00898; Wed, 30 Sep 2026 16:24:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790785475; bh=snov//ytzTXhmGpzjLg66K88O4vnjzLqPK/kZdMuBE4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=S47hz5pHqN8/tvV7d5CZ5Xn3G7+8cGkbZpSKblk7gmRhuzfogIZz+bUYLC5PC/UqP VM7H8fYyrjZPWgjKD/bNPmwRTTaxddmi9kPKLND+s1i7sMdbYGucKujRfNGooXOMYF GR2S9wCX5wlYp8VzaXe8SCBzVxAgi6GBgD+Sd474= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , David Ahern , Jakub Kicinski , Miguel Gazquez , Sasha Levin Subject: [PATCH 6.1 495/982] net: dst: introduce dst->dev_rcu Date: Wed, 30 Sep 2026 17:20:31 +0200 Message-ID: <20260930152427.413673500@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152416.775402466@linuxfoundation.org> References: <20260930152416.775402466@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Miguel Gazquez Signed-off-by: Sasha Levin --- include/net/dst.h | 16 +++++++++++----- net/core/dst.c | 2 +- net/ipv4/route.c | 4 ++-- 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/include/net/dst.h b/include/net/dst.h index 7c0cf856154de..96dd65a941c51 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; @@ -562,9 +565,12 @@ static inline struct net_device *dst_dev(const struct dst_entry *dst) 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); +} + +static inline struct net *dst_dev_net_rcu(const struct dst_entry *dst) +{ + return dev_net_rcu(dst_dev_rcu(dst)); } static inline struct net_device *skb_dst_dev(const struct sk_buff *skb) @@ -584,7 +590,7 @@ static inline struct net *skb_dst_dev_net(const struct sk_buff *skb) static inline struct net *skb_dst_dev_net_rcu(const struct sk_buff *skb) { - return dev_net_rcu(skb_dst_dev(skb)); + return dev_net_rcu(skb_dst_dev_rcu(skb)); } struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie); diff --git a/net/core/dst.c b/net/core/dst.c index 24a1cc3d2a084..cbb6888aa32ba 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; - WRITE_ONCE(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 a2985265c7929..e3cce307e0e9c 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(dst)); + 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(dst)); + 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(); -- 2.53.0