Commit 2dce8c52 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

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



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: 4a6ce2b6 ("net: introduce a new function dst_dev_put()")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250630121934.3399505-6-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent f1c5fd34

include/net/dst.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

}

include/net/lwtunnel.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

net/core/dst.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

net/ipv4/route.c

+1 −1
Original line number Diff line number Diff line
@@ -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);