netdev - Re: [PATCH net] net: bpf: fix request

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Date:   Thu, 9 Jun 2022 17:36:18 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Jon Maxwell <jmaxwell37@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, atenart@...nel.org, cutaylor-pub@...oo.com,
        alexei.starovoitov@...il.com, joe@...ium.io, i@....io,
        bpf@...r.kernel.org
Subject: Re: [PATCH net] net: bpf: fix request_sock leak in filter.c

On Thu, Jun 09, 2022 at 05:17:47PM -0700, Martin KaFai Lau wrote:
> On Thu, Jun 09, 2022 at 10:29:15PM +0200, Daniel Borkmann wrote:
> > On 6/9/22 3:18 AM, Jon Maxwell wrote:
> > > A customer reported a request_socket leak in a Calico cloud environment. We
> > > found that a BPF program was doing a socket lookup with takes a refcnt on
> > > the socket and that it was finding the request_socket but returning the parent
> > > LISTEN socket via sk_to_full_sk() without decrementing the child request socket
> > > 1st, resulting in request_sock slab object leak. This patch retains the
> Great catch and debug indeed!
> 
> > > existing behaviour of returning full socks to the caller but it also decrements
> > > the child request_socket if one is present before doing so to prevent the leak.
> > > 
> > > Thanks to Curtis Taylor for all the help in diagnosing and testing this. And
> > > thanks to Antoine Tenart for the reproducer and patch input.
> > > 
> > > Fixes: f7355a6c0497 bpf: ("Check sk_fullsock() before returning from bpf_sk_lookup()")
> > > Fixes: edbf8c01de5a bpf: ("add skc_lookup_tcp helper")
> Instead of the above commits, I think this dated back to
> 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF")

Since this is more bpf specific, I think it could go to the bpf tree.
In v2, please cc bpf@...r.kernel.org and tag it with 'PATCH v2 bpf'.