[PATCH net] ipv4: use WARN_ON_ONCE() in ip_rt_bug()

[PATCH net] ipv4: use WARN_ON_ONCE() in ip_rt_bug()

[Eric Dumazet]

It turns out ip_rt_bug() can be called more than expected.

syzbot will still panic (because of panic_on_warn=1), but non debug
kernels will no longer die while repeating stack traces on the console.

Fixes: c378a9c019cf ("ipv4: Give backtrace in ip_rt_bug().")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index bc1296f0ea69b0705e00e547a0d550129e03326a..3d62d45d84bda986db8b3592c0c7f5c81da3fb7e 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1272,7 +1272,7 @@ static int ip_rt_bug(struct net *net, struct sock *sk, struct sk_buff *skb)
 		 __func__, &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
 		 skb->dev ? skb->dev->name : "?");
 	kfree_skb(skb);
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 	return 0;
 }
 
-- 
2.54.0.631.ge1b05301d1-goog

Re: [PATCH net] ipv4: use WARN_ON_ONCE() in ip_rt_bug()

[David Ahern]

On 5/19/26 1:32 PM, Eric Dumazet wrote:
> It turns out ip_rt_bug() can be called more than expected.
> 
> syzbot will still panic (because of panic_on_warn=1), but non debug
> kernels will no longer die while repeating stack traces on the console.
> 
> Fixes: c378a9c019cf ("ipv4: Give backtrace in ip_rt_bug().")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv4/route.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 



Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH net] ipv4: use WARN_ON_ONCE() in ip_rt_bug()

[Jiayuan Chen]

On 5/20/26 3:32 AM, Eric Dumazet wrote:
> It turns out ip_rt_bug() can be called more than expected.
>
> syzbot will still panic (because of panic_on_warn=1), but non debug
> kernels will no longer die while repeating stack traces on the console.
>
> Fixes: c378a9c019cf ("ipv4: Give backtrace in ip_rt_bug().")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>   net/ipv4/route.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index bc1296f0ea69b0705e00e547a0d550129e03326a..3d62d45d84bda986db8b3592c0c7f5c81da3fb7e 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -1272,7 +1272,7 @@ static int ip_rt_bug(struct net *net, struct sock *sk, struct sk_buff *skb)
>   		 __func__, &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
>   		 skb->dev ? skb->dev->name : "?");
>   	kfree_skb(skb);
> -	WARN_ON(1);
> +	WARN_ON_ONCE(1);
>   	return 0;
>   }
>   


Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>


Recently I backported one missing patch to stable because of excessive
ip_rt_bug() prints. So I think it is reasonable to carry a Fixes tag for 
backporting.

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.6.y&id=da54b3039d436227deebbc202cefea63bd318a38