[PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

[PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

[Saurabh Sengar]

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@vger.kernel.org
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
 drivers/net/hyperv/netvsc_bpf.c | 2 +-
 drivers/net/hyperv/netvsc_drv.c | 2 --
 net/core/dev.c                  | 1 +
 3 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
index e01c5997a551..1dd3755d9e6d 100644
--- a/drivers/net/hyperv/netvsc_bpf.c
+++ b/drivers/net/hyperv/netvsc_bpf.c
@@ -183,7 +183,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)
 	xdp.command = XDP_SETUP_PROG;
 	xdp.prog = prog;
 
-	ret = dev_xdp_propagate(vf_netdev, &xdp);
+	ret = netif_xdp_propagate(vf_netdev, &xdp);
 
 	if (ret && prog)
 		bpf_prog_put(prog);
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index d8b169ac0343..ee3aaf9c10e6 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -2462,8 +2462,6 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
 
-	netvsc_vf_setxdp(vf_netdev, NULL);
-
 	reinit_completion(&net_device_ctx->vf_add);
 	netdev_rx_handler_unregister(vf_netdev);
 	netdev_upper_dev_unlink(vf_netdev, ndev);
diff --git a/net/core/dev.c b/net/core/dev.c
index fccf2167b235..8c6c9d7fba26 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9953,6 +9953,7 @@ int netif_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf)
 
 	return dev->netdev_ops->ndo_bpf(dev, bpf);
 }
+EXPORT_SYMBOL_GPL(netif_xdp_propagate);
 
 u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode)
 {
-- 
2.43.0

RE: [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

[Haiyang Zhang]

> -----Original Message-----
> From: Saurabh Sengar <ssengar@linux.microsoft.com>
> Sent: Saturday, May 17, 2025 11:48 PM
> To: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang
> <haiyangz@microsoft.com>; wei.liu@kernel.org; Dexuan Cui
> <decui@microsoft.com>; andrew+netdev@lunn.ch; davem@davemloft.net;
> edumazet@google.com; pabeni@redhat.com; horms@kernel.org; ast@kernel.org;
> daniel@iogearbox.net; hawk@kernel.org; john.fastabend@gmail.com;
> sdf@fomichev.me; kuniyu@amazon.com; ahmed.zaki@intel.com;
> aleksander.lobakin@intel.com; linux-hyperv@vger.kernel.org;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; bpf@vger.kernel.org
> Cc: Saurabh Singh Sengar <ssengar@microsoft.com>; stable@vger.kernel.org;
> Saurabh Sengar <ssengar@linux.microsoft.com>
> Subject: [PATCH net] hv_netvsc: fix potential deadlock in
> netvsc_vf_setxdp()
> 
> 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@vger.kernel.org
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>

Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>

Re: [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

[ALOK TIWARI]

On 18-05-2025 09:17, 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.

avoid noop and repetition (because the paragraph about net_shaper_ops is 
repeated):

"This deadlock was not observed so far because net_shaper_ops was never 
set, and thus the lock was effectively a no-op in this case. Fix this by 
using netif_xdp_propagate() instead of dev_xdp_propagate() to avoid 
recursive locking in this path.

Also, clean up the unregistration path by removing the unnecessary call 
to netvsc_vf_setxdp(), since unregister_netdevice_many_notify() already 
performs this cleanup via dev_xdp_uninstall()."

> 
> 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@vger.kernel.org
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
>   drivers/net/hyperv/netvsc_bpf.c | 2 +-
>   drivers/net/hyperv/netvsc_drv.c | 2 --
>   net/core/dev.c                  | 1 +
>   3 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c
> index e01c5997a551..1dd3755d9e6d 100644
> --- a/drivers/net/hyperv/netvsc_bpf.c
> +++ b/drivers/net/hyperv/netvsc_bpf.c
> @@ -183,7 +183,7 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog)


Thanks,
Alok

Re: [PATCH net] hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()

[Erni Sri Satya Vennela]

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@vger.kernel.org
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---

Built and booted successfully. 

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

Thanks!