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Message-ID: <604aa161-9648-41bd-9ede-940e51f7248c@linux.dev>
Date: Fri, 4 Oct 2024 17:36:51 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski
<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, eric.dumazet@...il.com,
netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/5] net: add TIME_WAIT logic to sk_to_full_sk()
On 10/4/24 2:56 PM, Eric Dumazet wrote:
> On Fri, Oct 4, 2024 at 9:16 PM Eric Dumazet <edumazet@...gle.com> wrote:
>>
>> TCP will soon attach TIME_WAIT sockets to some ACK and RST.
>>
>> Make sure sk_to_full_sk() detects this and does not return
>> a non full socket.
>>
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> ---
>> include/net/inet_sock.h | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
>> index 394c3b66065e20d34594d6e2a2010c55bb457810..cec093b78151b9a3b95ad4b3672a72b0aa9a8305 100644
>> --- a/include/net/inet_sock.h
>> +++ b/include/net/inet_sock.h
>> @@ -319,8 +319,10 @@ static inline unsigned long inet_cmsg_flags(const struct inet_sock *inet)
>> static inline struct sock *sk_to_full_sk(struct sock *sk)
>> {
>> #ifdef CONFIG_INET
>> - if (sk && sk->sk_state == TCP_NEW_SYN_RECV)
>> + if (sk && READ_ONCE(sk->sk_state) == TCP_NEW_SYN_RECV)
>> sk = inet_reqsk(sk)->rsk_listener;
>> + if (sk && READ_ONCE(sk->sk_state) == TCP_TIME_WAIT)
>> + sk = NULL;
>> #endif
>> return sk;
>> }
>
> It appears some callers do not check if the return value could be NULL.
> I will have to add in v2 :
>
> diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> index ce91d9b2acb9f8991150ceead4475b130bead438..c3ffb45489a6924c1bc80355e862e243ec195b01
> 100644
> --- a/include/linux/bpf-cgroup.h
> +++ b/include/linux/bpf-cgroup.h
> @@ -209,7 +209,7 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk,
> int __ret = 0; \
> if (cgroup_bpf_enabled(CGROUP_INET_EGRESS) && sk) { \
The above "&& sk" test can probably be removed after the "__sk &&" addition below.
> typeof(sk) __sk = sk_to_full_sk(sk); \
> - if (sk_fullsock(__sk) && __sk == skb_to_full_sk(skb) && \
> + if (__sk && sk_fullsock(__sk) && __sk == skb_to_full_sk(skb) && \
sk_to_full_sk() includes the TCP_TIME_WAIT check now. I wonder if testing __sk
for NULL is good enough and the sk_fullsock(__sk) check can be removed also.
Thanks for working on this series. It is useful for the bpf prog.
> cgroup_bpf_sock_enabled(__sk, CGROUP_INET_EGRESS)) \
> __ret = __cgroup_bpf_run_filter_skb(__sk, skb, \
> CGROUP_INET_EGRESS); \
> diff --git a/net/core/filter.c b/net/core/filter.c
> index bd0d08bf76bb8de39ca2ca89cda99a97c9b0a034..533025618b2c06efa31548708f21d9e0ccbdc68d
> 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6778,7 +6778,7 @@ __bpf_sk_lookup(struct sk_buff *skb, struct
> bpf_sock_tuple *tuple, u32 len,
> /* 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 (!sk_fullsock(sk2))
> + if (sk2 && !sk_fullsock(sk2))
> sk2 = NULL;
> if (sk2 != sk) {
> sock_gen_put(sk);
> @@ -6826,7 +6826,7 @@ bpf_sk_lookup(struct sk_buff *skb, struct
> bpf_sock_tuple *tuple, u32 len,
> /* 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 (!sk_fullsock(sk2))
> + if (sk2 && !sk_fullsock(sk2))
> sk2 = NULL;
> if (sk2 != sk) {
> sock_gen_put(sk);
> @@ -7276,7 +7276,7 @@ BPF_CALL_1(bpf_get_listener_sock, struct sock *, sk)
> {
> sk = sk_to_full_sk(sk);
>
> - if (sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_RCU_FREE))
> + if (sk && sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_RCU_FREE))
> return (unsigned long)sk;
>
> return (unsigned long)NULL;
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