linux-kernel - Re: [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf

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Message-ID: <20250521084141.GA10135@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
Date: Wed, 21 May 2025 01:41:41 -0700
From: Erni Sri Satya Vennela <ernis@...ux.microsoft.com>
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] hv_netvsc: fix potential deadlock in
 netvsc_vf_setxdp()

On Sat, May 17, 2025 at 08:47:50PM -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 and this lock in noop in this case. Fix this by using
> netif_xdp_propagate instead of dev_xdp_propagate to avoid recursive
> locking in this path.
> 
> This issue has not observed so far because net_shaper_ops was unset,
> making the lock path effectively a no-op. To prevent recursive locking
> and avoid this deadlock, replace dev_xdp_propagate() with
> netif_xdp_propagate(), which does not acquire the lock again.
> 
> Also, clean up the unregistration path by removing unnecessary call to
> netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already
> performs this cleanup via dev_xdp_uninstall.
> 
> Fixes: 97246d6d21c2 ("net: hold netdev instance lock during ndo_bpf")
> Cc: stable@...r.kernel.org
> Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
> ---

Built and booted successfully. 

Tested-by: Erni Sri Satya Vennela <ernis@...ux.microsoft.com> 

Thanks!