# \[PATCH net-next v2 2/5\] hv\_netvsc: hold the VF's instance lock when installing XDP on it - From: Jakub Kicinski \ - Date: 2026-11-09 19:48:50 - List: netdev - Page: https://ratatoskr.run/netdev/2026/11/17899688 - Thread: https://ratatoskr.run/netdev/2026/11/17899693/t.md ```text netvsc_vf_setxdp() has two kinds of callers. netvsc_register_vf() runs with the VF's instance lock already held, either by the NETDEV_REGISTER notifier or by netvsc_probe() taking it, which is why the propagation moved to the caller-locked netif_xdp_propagate(). netvsc_bpf() runs with just RTNL, so the VF's ndo_bpf() gets called unlocked. For a VF with an ops lock that trips the lockdep assertion in dev_get_min_mp_channel_count(), which netif_xdp_propagate() calls, and races with binding a memory provider, which takes only the instance lock. Take the VF's lock in netvsc_bpf(). Reported by Sashiko during core rework, the race was not reproduced. Cc: stable+noautosel@kernel.org # LLM report + LLM fix, untested Fixes: 3ec523304976 ("hv_netvsc: fix potential deadlock in netvsc_vf_setxdp()") Signed-off-by: Jakub Kicinski Tested-by: Kameron Carr Tested-by: Erni Sri Satya Vennela --- v2: - commit msg: say that the race was not reproduced, rather than that the fix is untested, as functional testing covered it v1: https://lore.kernel.org/20261001014131.310771-3-kuba@kernel.org --- drivers/net/hyperv/netvsc_bpf.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/net/hyperv/netvsc_bpf.c b/drivers/net/hyperv/netvsc_bpf.c index fcc60729384e..ec8edfaebf0b 100644 --- a/drivers/net/hyperv/netvsc_bpf.c +++ b/drivers/net/hyperv/netvsc_bpf.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -162,6 +163,7 @@ int netvsc_xdp_set(struct net_device *dev, struct bpf_prog *prog, return 0; } +/* Caller holds the VF's lock, see netdev_lock_ops() */ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog) { struct netdev_bpf xdp; @@ -172,6 +174,8 @@ int netvsc_vf_setxdp(struct net_device *vf_netdev, struct bpf_prog *prog) if (!vf_netdev) return 0; + netdev_assert_locked_ops_compat(vf_netdev); + if (!vf_netdev->netdev_ops->ndo_bpf) return 0; @@ -218,7 +222,15 @@ int netvsc_bpf(struct net_device *dev, struct netdev_bpf *bpf) if (ret) goto put_old_prog; - ret = netvsc_vf_setxdp(vf_netdev, bpf->prog); + /* Unlike netvsc_register_vf() we don't get the VF's lock + * handed to us here. + */ + ret = 0; + if (vf_netdev) { + netdev_lock_ops(vf_netdev); + ret = netvsc_vf_setxdp(vf_netdev, bpf->prog); + netdev_unlock_ops(vf_netdev); + } if (ret) { netdev_err(dev, "vf_setxdp failed:%d\n", ret); -- 2.56.0 ```