netdev - Re: [PATCH bpf 1/2] bpf: sockmap, af_unix sockets need to hold ref for pair sock

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Message-ID: <bc92c670-f472-43b1-af0b-a50353ed8757@linux.dev>
Date: Mon, 20 Nov 2023 13:13:18 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: John Fastabend <john.fastabend@...il.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, yangyingliang@...wei.com,
 martin.lau@...nel.org, Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH bpf 1/2] bpf: sockmap, af_unix sockets need to hold ref
 for pair sock

On 11/6/23 4:35 AM, Jakub Sitnicki wrote:
>> diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c
>> index 2f9d8271c6ec..705eeed10be3 100644
>> --- a/net/unix/unix_bpf.c
>> +++ b/net/unix/unix_bpf.c
>> @@ -143,6 +143,8 @@ static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
>>   
>>   int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
>>   {
>> +	struct sock *skpair;
>> +
>>   	if (sk->sk_type != SOCK_DGRAM)
>>   		return -EOPNOTSUPP;
>>   
>> @@ -152,6 +154,9 @@ int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool re
>>   		return 0;
>>   	}
>>   
>> +	skpair = unix_peer(sk);
>> +	sock_hold(skpair);
>> +	psock->skpair = skpair;
>>   	unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
>>   	sock_replace_proto(sk, &unix_dgram_bpf_prot);
>>   	return 0;
> unix_dgram should not need this, since it grabs a ref on each sendmsg.

John, could you address this comment and respin v2?

The unix_inet_redir_to_connected() seems needing a fix in patch 2 also as 
pointed out by JakubS.

Thanks.

> 
> I'm not able to reproduce this bug for unix_dgram.
> 
> Have you seen any KASAN reports for unix_dgram from syzcaller?