On 2025-05-21 at 10:25:03, Saurabh Sengar (ssen...@linux.microsoft.com) 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 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().
>
> Fixes: 97246d6d21c2 ("net: hold netdev instance lock during ndo_bpf")
> Cc: sta...@vger.kernel.org
> Signed-off-by: Saurabh Sengar <ssen...@linux.microsoft.com>
> Tested-by: Erni Sri Satya Vennela <er...@linux.microsoft.com>
> Reviewed-by: Haiyang Zhang <haiya...@microsoft.com>
Reviewed-by: Subbaraya Sundeep <sbha...@marvell.com>
Thanks,
Sundeep
> ---
> [V2]
> - Modified commit message
>
> 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
>
