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net: dst: add four helpers to annotate data-races around dst->dev

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dst->dev is read locklessly in many contexts,
and written in dst_dev_put().

Fixing all the races is going to need many changes.

We probably will have to add full RCU protection.

Add three helpers to ease this painful process.

static inline struct net_device *dst_dev(const struct dst_entry *dst)
{
       return READ_ONCE(dst->dev);
}

static inline struct net_device *skb_dst_dev(const struct sk_buff *skb)
{
       return dst_dev(skb_dst(skb));
}

static inline struct net *skb_dst_dev_net(const struct sk_buff *skb)
{
       return dev_net(skb_dst_dev(skb));
}

static inline struct net *skb_dst_dev_net_rcu(const struct sk_buff *skb)
{
       return dev_net_rcu(skb_dst_dev(skb));
}

Fixes: 4a6ce2b6f2 ("net: introduce a new function dst_dev_put()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250630121934.3399505-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-06-30 12:19:30 +00:00 • committed by Jakub Kicinski
parent 2dce8c52a9
commit 88fe14253e
3 changed files with 26 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

20
include/net/dst.h
View file

@ -563,6 +563,26 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu)
dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
}
static inline struct net_device *dst_dev(const struct dst_entry *dst)
{
return READ_ONCE(dst->dev);
}
static inline struct net_device *skb_dst_dev(const struct sk_buff *skb)
{
return dst_dev(skb_dst(skb));
}
static inline struct net *skb_dst_dev_net(const struct sk_buff *skb)
{
return dev_net(skb_dst_dev(skb));
}
static inline struct net *skb_dst_dev_net_rcu(const struct sk_buff *skb)
{
return dev_net_rcu(skb_dst_dev(skb));
}
struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie);
void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu, bool confirm_neigh);

4
net/core/dst.c
View file

@ -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);
dst->dev = blackhole_netdev;
WRITE_ONCE(dst->dev, blackhole_netdev);
netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker,
GFP_ATOMIC);
}
@ -263,7 +263,7 @@ unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
{
unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
return mtu ? : dst->dev->mtu;
return mtu ? : dst_dev(dst)->mtu;
}
EXPORT_SYMBOL_GPL(dst_blackhole_mtu);

8
net/core/sock.c
View file

@ -2588,8 +2588,8 @@ static u32 sk_dst_gso_max_size(struct sock *sk, struct dst_entry *dst)
!ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr));
#endif
/* pairs with the WRITE_ONCE() in netif_set_gso(_ipv4)_max_size() */
max_size = is_ipv6 ? READ_ONCE(dst->dev->gso_max_size) :
READ_ONCE(dst->dev->gso_ipv4_max_size);
max_size = is_ipv6 ? READ_ONCE(dst_dev(dst)->gso_max_size) :
READ_ONCE(dst_dev(dst)->gso_ipv4_max_size);
if (max_size > GSO_LEGACY_MAX_SIZE && !sk_is_tcp(sk))
max_size = GSO_LEGACY_MAX_SIZE;
@ -2600,7 +2600,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
{
u32 max_segs = 1;
sk->sk_route_caps = dst->dev->features;
sk->sk_route_caps = dst_dev(dst)->features;
if (sk_is_tcp(sk)) {
struct inet_connection_sock *icsk = inet_csk(sk);
@ -2618,7 +2618,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
sk->sk_gso_max_size = sk_dst_gso_max_size(sk, dst);
/* pairs with the WRITE_ONCE() in netif_set_gso_max_segs() */
max_segs = max_t(u32, READ_ONCE(dst->dev->gso_max_segs), 1);
max_segs = max_t(u32, READ_ONCE(dst_dev(dst)->gso_max_segs), 1);
}
}
sk->sk_gso_max_segs = max_segs;