netdev - Re: [PATCH v2 net] l2tp: do not use inet_hash()/inet

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Date:   Sat, 30 May 2020 21:56:13 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        jchapman@...alix.com, andriin@...com,
        syzbot+3610d489778b57cc8031@...kaller.appspotmail.com
Subject: Re: [PATCH v2 net] l2tp: do not use inet_hash()/inet_unhash()

From: Eric Dumazet <edumazet@...gle.com>
Date: Fri, 29 May 2020 11:20:53 -0700

> syzbot recently found a way to crash the kernel [1]
> 
> Issue here is that inet_hash() & inet_unhash() are currently
> only meant to be used by TCP & DCCP, since only these protocols
> provide the needed hashinfo pointer.
> 
> L2TP uses a single list (instead of a hash table)
> 
> This old bug became an issue after commit 610236587600
> ("bpf: Add new cgroup attach type to enable sock modifications")
> since after this commit, sk_common_release() can be called
> while the L2TP socket is still considered 'hashed'.
 ...
> Fixes: 0d76751fad77 ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: James Chapman <jchapman@...alix.com>
> Cc: Andrii Nakryiko <andriin@...com>
> Reported-by: syzbot+3610d489778b57cc8031@...kaller.appspotmail.com

Applied and queued up for -stable, thanks.