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

From: John Fastabend <[email-masked]>
Date: Tue, 21 Nov 2023 12:40:45 -0800

Martin KaFai Lau wrote:
> 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?

Respinning now just letting some tests run for a bit and I'll kick it out.

Thanks.

> 
> 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?