netdev - Re: [PATCH net,v2] hv_netvsc: fix potential deadlock in netvsc_vf

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Message-ID: <20250522151346.57390f40@kernel.org>
Date: Thu, 22 May 2025 15:13:46 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Saurabh Sengar <ssengar@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
 decui@...rosoft.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, pabeni@...hat.com, horms@...nel.org, ast@...nel.org,
 daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
 sdf@...ichev.me, kuniyu@...zon.com, ahmed.zaki@...el.com,
 aleksander.lobakin@...el.com, linux-hyperv@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 ssengar@...rosoft.com, stable@...r.kernel.org
Subject: Re: [PATCH net,v2] hv_netvsc: fix potential deadlock in
 netvsc_vf_setxdp()

On Wed, 21 May 2025 03:25:03 -0700 Saurabh Sengar wrote:
> The MANA driver's probe registers netdevice via the following call chain:
> 
> mana_probe()
>   register_netdev()
>     register_netdevice()
> 
> register_netdevice() calls notifier callback for netvsc driver,
> holding the netdev mutex via netdev_lock_ops().
> 
> Further this netvsc notifier callback end up attempting to acquire the
> same lock again in dev_xdp_propagate() leading to deadlock.
> 
> netvsc_netdev_event()
>   netvsc_vf_setxdp()
>     dev_xdp_propagate()
> 
> This deadlock was not observed so far because net_shaper_ops was never set,

The lock is on the VF, I think you meant to say that no device you use
in Azure is ops locked?

There's also the call to netvsc_register_vf() on probe path, please
fix or explain why it doesn't need locking in the commit message.
-- 
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