6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit caedcc5b6df1b2e2b5f39079e3369c1d4d5c5f50 ]
Followup of commit 88fe14253e1818 ("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()") Cc: stable@vger.kernel.org Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: David Ahern dsahern@kernel.org Link: https://patch.msgid.link/20250828195823.3958522-2-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Stable-dep-of: 50c127a69cd62 ("Replace three dst_dev() with a lockdep enabled helper.") Signed-off-by: Gyokhan Kochmarla gyokhan@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/dst.h | 16 +++++++++++----- net/core/dst.c | 2 +- net/ipv4/route.c | 4 ++-- 3 files changed, 14 insertions(+), 8 deletions(-)
--- a/include/net/dst.h +++ b/include/net/dst.h @@ -24,7 +24,10 @@ 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; @@ -568,9 +571,12 @@ static inline struct net_device *dst_dev
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) @@ -590,7 +596,7 @@ static inline struct net *skb_dst_dev_ne
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); --- a/net/core/dst.c +++ b/net/core/dst.c @@ -150,7 +150,7 @@ void dst_dev_put(struct dst_entry *dst) dst->ops->ifdown(dst, dev); WRITE_ONCE(dst->input, dst_discard); WRITE_ONCE(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); } --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1030,7 +1030,7 @@ static void __ip_rt_update_pmtu(struct r 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); @@ -1328,7 +1328,7 @@ static unsigned int ipv4_default_advmss( 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();