netdev - Re: [PATCH bpf-next v3 04/12] tcp_bpf: Don't let child socket inherit parent protocol ops on copy

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Message-ID: <878sly31i5.fsf@cloudflare.com>
Date:   Thu, 23 Jan 2020 11:34:10 +0100
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Martin Lau <kafai@...com>
Cc:     "bpf\@vger.kernel.org" <bpf@...r.kernel.org>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team\@cloudflare.com" <kernel-team@...udflare.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "John Fastabend" <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCH bpf-next v3 04/12] tcp_bpf: Don't let child socket inherit parent protocol ops on copy

On Wed, Jan 22, 2020 at 09:35 PM CET, Martin Lau wrote:
> On Wed, Jan 22, 2020 at 02:05:41PM +0100, Jakub Sitnicki wrote:
>> Prepare for cloning listening sockets that have their protocol callbacks
>> overridden by sk_msg. Child sockets must not inherit parent callbacks that
>> access state stored in sk_user_data owned by the parent.
>> 
>> Restore the child socket protocol callbacks before it gets hashed and any
>> of the callbacks can get invoked.
>> 
>> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
>> ---
>>  include/net/tcp.h        |  7 +++++++
>>  net/ipv4/tcp_bpf.c       | 13 +++++++++++++
>>  net/ipv4/tcp_minisocks.c |  2 ++
>>  3 files changed, 22 insertions(+)
>> 
>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>> index 9dd975be7fdf..ac205d31e4ad 100644
>> --- a/include/net/tcp.h
>> +++ b/include/net/tcp.h
>> @@ -2181,6 +2181,13 @@ int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
>>  		    int nonblock, int flags, int *addr_len);
>>  int __tcp_bpf_recvmsg(struct sock *sk, struct sk_psock *psock,
>>  		      struct msghdr *msg, int len, int flags);
>> +#ifdef CONFIG_NET_SOCK_MSG
>> +void tcp_bpf_clone(const struct sock *sk, struct sock *child);
> nit.  "struct sock *child" vs ...
>
>> +#else
>> +static inline void tcp_bpf_clone(const struct sock *sk, struct sock *child)
>> +{
>> +}
>> +#endif
>>  
>>  /* Call BPF_SOCK_OPS program that returns an int. If the return value
>>   * is < 0, then the BPF op failed (for example if the loaded BPF
>> diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
>> index 4f25aba44ead..16060e0893a1 100644
>> --- a/net/ipv4/tcp_bpf.c
>> +++ b/net/ipv4/tcp_bpf.c
>> @@ -582,6 +582,19 @@ static void tcp_bpf_close(struct sock *sk, long timeout)
>>  	saved_close(sk, timeout);
>>  }
>>  
>> +/* If a child got cloned from a listening socket that had tcp_bpf
>> + * protocol callbacks installed, we need to restore the callbacks to
>> + * the default ones because the child does not inherit the psock state
>> + * that tcp_bpf callbacks expect.
>> + */
>> +void tcp_bpf_clone(const struct sock *sk, struct sock *newsk)
> "struct sock *newsk" here.
>
> Could be a follow-up.
>
> Other than that,
> Acked-by: Martin KaFai Lau <kafai@...com>

Will fix in v4. Thanks!