netdev - Re: [PATCH bpf] xdp: fix potential deadlock on socket mutex

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Date:   Fri, 12 Jul 2019 15:07:51 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Ilya Maximets <i.maximets@...sung.com>, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        xdp-newbies@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH bpf] xdp: fix potential deadlock on socket mutex

On 07/08/2019 01:03 PM, Ilya Maximets wrote:
> There are 2 call chains:
> 
>   a) xsk_bind --> xdp_umem_assign_dev
>   b) unregister_netdevice_queue --> xsk_notifier
> 
> with the following locking order:
> 
>   a) xs->mutex --> rtnl_lock
>   b) rtnl_lock --> xdp.lock --> xs->mutex
> 
> Different order of taking 'xs->mutex' and 'rtnl_lock' could produce a
> deadlock here. Fix that by moving the 'rtnl_lock' before 'xs->lock' in
> the bind call chain (a).
> 
> Reported-by: syzbot+bf64ec93de836d7f4c2c@...kaller.appspotmail.com
> Fixes: 455302d1c9ae ("xdp: fix hang while unregistering device bound to xdp socket")
> Signed-off-by: Ilya Maximets <i.maximets@...sung.com>

Applied, thanks!