6.6-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 2dce8c52a98995c4719def6f88629ab1581c0b82 ]
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: 4a6ce2b6f2ec ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/dst.h | 2 +- include/net/lwtunnel.h | 4 ++-- net/core/dst.c | 2 +- net/ipv4/route.c | 2 +- 4 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/net/dst.h b/include/net/dst.h index ef7f88f01881..60fb5d2faf43 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -464,7 +464,7 @@ 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); } diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h index a4632a64daae..09791f5d9b6e 100644 --- a/include/net/lwtunnel.h +++ b/include/net/lwtunnel.h @@ -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); diff --git a/net/core/dst.c b/net/core/dst.c index def3dbbd37e3..2513665696f6 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -151,7 +151,7 @@ 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); diff --git a/net/ipv4/route.c b/net/ipv4/route.c index f8538507ce3f..6ee77f7f9114 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1700,7 +1700,7 @@ 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);