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From: Kui-Feng Lee <sinquersw@gmail.com>
To: Martin KaFai Lau <martin.lau@linux.dev>,
	Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org,
	daniel@iogearbox.net, davem@davemloft.net, dsahern@kernel.org,
	edumazet@google.com, haoluo@google.com, john.fastabend@gmail.com,
	jolsa@kernel.org, kpsingh@kernel.org, kuba@kernel.org,
	kuni1840@gmail.com, mykolal@fb.com, netdev@vger.kernel.org,
	pabeni@redhat.com, sdf@google.com, song@kernel.org,
	yonghong.song@linux.dev
Subject: Re: [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks.
Date: Mon, 23 Oct 2023 17:37:26 -0700	[thread overview]
Message-ID: <9aebb3e9-70c5-428c-bc31-7b38a04e4848@gmail.com> (raw)
In-Reply-To: <42d66dde-29d6-f948-bc2e-72465beb800f@linux.dev>



On 10/23/23 14:35, Martin KaFai Lau wrote:
> On 10/20/23 11:48 PM, Kuniyuki Iwashima wrote:
>> I think this was doable.  With the diff below, I was able to skip
>> validation in cookie_v[46]_check() when if skb->sk is not NULL.
>>
>> The kfunc allocates req and set req->syncookie to 1, which is usually
>> set in TX path, so if it's 1 in RX (inet_steal_sock()), we can see
>> that req is allocated by kfunc (at least, req->syncookie &&
>> req->rsk_listener never be true in the current TCP stack).
>>
>> The difference here is that req allocated by kfunc holds refcnt of
>> rsk_listener (passing true to inet_reqsk_alloc()) to prevent freeing
>> the listener until req reaches cookie_v[46]_check().
> 
> The cookie_v[46]_check() holds the listener sk refcnt now?


The caller of cookie_v[46]_check() should hold a refcnt of the listener.
If the listener is destroyed, the callers of cookie_v[46]_check() should
fail to lookup a sock for the skb. However, in this case, the kfunc sets
a sock to skb->sk, and the lookup function
(__inet_lookup_skb()) steals sock from skb. So, there is no guarantee
ensuring the listener is still alive.

One solution is let the stealing function to lookup the listener if
inet_reqsk(skb->sk)->syncookie is true.

  reply	other threads:[~2023-10-24  0:37 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-13 22:04 [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 01/11] tcp: Clean up reverse xmas tree in cookie_v[46]_check() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 02/11] tcp: Cache sock_net(sk) " Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 03/11] tcp: Clean up goto labels " Kuniyuki Iwashima
2023-10-17  0:00   ` Kui-Feng Lee
2023-10-17  0:30     ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 04/11] tcp: Don't initialise tp->tsoffset in tcp_get_cookie_sock() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 05/11] bpf: tcp: Add SYN Cookie generation SOCK_OPS hook Kuniyuki Iwashima
2023-10-18  0:54   ` Martin KaFai Lau
2023-10-18 17:00     ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 06/11] bpf: tcp: Add SYN Cookie validation " Kuniyuki Iwashima
2023-10-16 20:38   ` Stanislav Fomichev
2023-10-16 22:02     ` Kuniyuki Iwashima
2023-10-17 16:52   ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 07/11] bpf: Make bpf_sock_ops.replylong[1] writable Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 08/11] bpf: tcp: Make TS available for SYN Cookie storage Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 09/11] tcp: Split cookie_ecn_ok() Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 10/11] bpf: tcp: Make WS, SACK, ECN configurable from BPF SYN Cookie Kuniyuki Iwashima
2023-10-18  1:08   ` Martin KaFai Lau
2023-10-18 17:02     ` Kuniyuki Iwashima
2023-10-13 22:04 ` [PATCH v1 bpf-next 11/11] selftest: bpf: Test BPF_SOCK_OPS_(GEN|CHECK)_SYNCOOKIE_CB Kuniyuki Iwashima
2023-10-17  5:50   ` Martin KaFai Lau
2023-10-17 16:29     ` Kuniyuki Iwashima
2023-10-16 13:05 ` [PATCH v1 bpf-next 00/11] bpf: tcp: Add SYN Cookie generation/validation SOCK_OPS hooks Daniel Borkmann
2023-10-16 16:11   ` Kuniyuki Iwashima
2023-10-16 14:19 ` Willem de Bruijn
2023-10-16 16:46   ` Kuniyuki Iwashima
2023-10-16 18:41     ` Willem de Bruijn
2023-10-17  5:53 ` Martin KaFai Lau
2023-10-17 16:48   ` Kuniyuki Iwashima
2023-10-18  6:19     ` Martin KaFai Lau
2023-10-18  8:02       ` Eric Dumazet
2023-10-18 17:20         ` Kuniyuki Iwashima
2023-10-18 21:47           ` Kui-Feng Lee
2023-10-18 22:31             ` Kuniyuki Iwashima
2023-10-19  7:25               ` Martin KaFai Lau
2023-10-19 18:01                 ` Kuniyuki Iwashima
2023-10-20 19:59                   ` Martin KaFai Lau
2023-10-20 23:10                     ` Kuniyuki Iwashima
2023-10-21  6:48                       ` Kuniyuki Iwashima
2023-10-23 21:35                         ` Martin KaFai Lau
2023-10-24  0:37                           ` Kui-Feng Lee [this message]
2023-10-24  1:22                             ` Kuniyuki Iwashima
2023-10-24 17:55                               ` Kui-Feng Lee

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