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net: dst: annotate data-races around dst->output

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dst_dev_put() can overwrite dst->output while other
cpus might read this field (for instance from dst_output())

Add READ_ONCE()/WRITE_ONCE() annotations to suppress
potential issues.

We will likely need RCU protection in the future.

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/20250630121934.3399505-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2025-06-30 12:19:29 +00:00
committed by Jakub Kicinski
parent f1c5fd3489
commit 2dce8c52a9
4 changed files with 5 additions and 5 deletions
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2
include/net/dst.h
View File

@@ -458,7 +458,7 @@ INDIRECT_CALLABLE_DECLARE(int ip_output(struct net *, struct sock *,
/* Output packet to network from transport. */
static inline int dst_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
return INDIRECT_CALL_INET(skb_dst(skb)->output,
return INDIRECT_CALL_INET(READ_ONCE(skb_dst(skb)->output),
ip6_output, ip_output,
net, sk, skb);
}

4
include/net/lwtunnel.h
View File

@@ -138,8 +138,8 @@ int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len,
static inline void lwtunnel_set_redirect(struct dst_entry *dst)
{
if (lwtunnel_output_redirect(dst->lwtstate)) {
dst->lwtstate->orig_output = dst->output;
dst->output = lwtunnel_output;
dst->lwtstate->orig_output = READ_ONCE(dst->output);
WRITE_ONCE(dst->output, lwtunnel_output);
}
if (lwtunnel_input_redirect(dst->lwtstate)) {
dst->lwtstate->orig_input = READ_ONCE(dst->input);

2
net/core/dst.c
View File

@@ -149,7 +149,7 @@ void dst_dev_put(struct dst_entry *dst)
if (dst->ops->ifdown)
dst->ops->ifdown(dst, dev);
WRITE_ONCE(dst->input, dst_discard);
dst->output = dst_discard_out;
WRITE_ONCE(dst->output, dst_discard_out);
dst->dev = blackhole_netdev;
netdev_ref_replace(dev, blackhole_netdev, &dst->dev_tracker,
GFP_ATOMIC);

2
net/ipv4/route.c
View File

@@ -1688,7 +1688,7 @@ struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
new_rt->rt_gw6 = rt->rt_gw6;
new_rt->dst.input = READ_ONCE(rt->dst.input);
new_rt->dst.output = rt->dst.output;
new_rt->dst.output = READ_ONCE(rt->dst.output);
new_rt->dst.error = rt->dst.error;
new_rt->dst.lastuse = jiffies;
new_rt->dst.lwtstate = lwtstate_get(rt->dst.lwtstate);