Re: [PATCH bpf 2/3] bpf: Extract shared reqsk-to-listener upgrade

[Emil Tsalapatis]

On Thu Jul 23, 2026 at 7:33 AM EDT, Michal Luczaj wrote:
> __bpf_sk_lookup() and bpf_sk_lookup() duplicate the same sk_to_full_sk()
> reqsk-to-listener upgrade. Extract it into a helper.
>
> Leave the currently unreachable WARN_ONCE as a defensive assert.
>
> No functional change.

Reviewed-by: Emil Tsalapatis <emil@xxxxxxxxxxxxxxx>

>
> Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
> ---
>  net/core/filter.c | 57 ++++++++++++++++++++++++-------------------------------
>  1 file changed, 25 insertions(+), 32 deletions(-)
>
> diff --git a/net/core/filter.c b/net/core/filter.c
> index b446aa8be5c3..403aba3ce891 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -7074,6 +7074,27 @@ __bpf_skc_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
>  	return sk;
>  }
>  
> +static struct sock *
> +bpf_sk_lookup_full_sk(struct sock *sk)
> +{
> +	struct sock *sk2 = sk_to_full_sk(sk);
> +
> +	/* sk_to_full_sk() may return sk->rsk_listener, make sure the original
> +	 * sk sock refcnt is decremented to prevent a request_sock leak.
> +	 */
> +	if (sk2 != sk) {
> +		sock_gen_put(sk);
> +		/* Ensure there is no need to bump sk2 refcnt. */
> +		if (unlikely(sk2 && !sock_flag(sk2, SOCK_RCU_FREE))) {
> +			WARN_ONCE(1, "Found non-RCU, unreferenced socket!");
> +			return NULL;
> +		}
> +		sk = sk2;
> +	}
> +
> +	return sk;
> +}
> +
>  static struct sock *
>  __bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
>  		struct net *caller_net, u32 ifindex, u8 proto, u64 netns_id,
> @@ -7083,22 +7104,8 @@ __bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
>  					   ifindex, proto, netns_id, flags,
>  					   sdif);
>  
> -	if (sk) {
> -		struct sock *sk2 = sk_to_full_sk(sk);
> -
> -		/* sk_to_full_sk() may return (sk)->rsk_listener, so make sure the original sk
> -		 * sock refcnt is decremented to prevent a request_sock leak.
> -		 */
> -		if (sk2 != sk) {
> -			sock_gen_put(sk);
> -			/* Ensure there is no need to bump sk2 refcnt */
> -			if (unlikely(sk2 && !sock_flag(sk2, SOCK_RCU_FREE))) {
> -				WARN_ONCE(1, "Found non-RCU, unreferenced socket!");
> -				return NULL;
> -			}
> -			sk = sk2;
> -		}
> -	}
> +	if (sk)
> +		sk = bpf_sk_lookup_full_sk(sk);
>  
>  	return sk;
>  }
> @@ -7129,22 +7136,8 @@ bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
>  	struct sock *sk = bpf_skc_lookup(skb, tuple, len, proto, netns_id,
>  					 flags);
>  
> -	if (sk) {
> -		struct sock *sk2 = sk_to_full_sk(sk);
> -
> -		/* sk_to_full_sk() may return (sk)->rsk_listener, so make sure the original sk
> -		 * sock refcnt is decremented to prevent a request_sock leak.
> -		 */
> -		if (sk2 != sk) {
> -			sock_gen_put(sk);
> -			/* Ensure there is no need to bump sk2 refcnt */
> -			if (unlikely(sk2 && !sock_flag(sk2, SOCK_RCU_FREE))) {
> -				WARN_ONCE(1, "Found non-RCU, unreferenced socket!");
> -				return NULL;
> -			}
> -			sk = sk2;
> -		}
> -	}
> +	if (sk)
> +		sk = bpf_sk_lookup_full_sk(sk);
>  
>  	return sk;
>  }