From: Haiyang Zhang haiyangz@microsoft.com

The existing code move the VF NIC to new namespace when NETDEV_REGISTER is received on netvsc NIC. During deletion of the namespace, default_device_exit_batch() >> default_device_exit_net() is called. When netvsc NIC is moved back and registered to the default namespace, it automatically brings VF NIC back to the default namespace. This will cause the default_device_exit_net() >> for_each_netdev_safe loop unable to detect the list end, and hit NULL ptr:

[ 231.449420] mana 7870:00:00.0 enP30832s1: Moved VF to namespace with: eth0 [ 231.449656] BUG: kernel NULL pointer dereference, address: 0000000000000010 [ 231.450246] #PF: supervisor read access in kernel mode [ 231.450579] #PF: error_code(0x0000) - not-present page [ 231.450916] PGD 17b8a8067 P4D 0 [ 231.451163] Oops: Oops: 0000 [#1] SMP NOPTI [ 231.451450] CPU: 82 UID: 0 PID: 1394 Comm: kworker/u768:1 Not tainted 6.16.0-rc4+ #3 VOLUNTARY [ 231.452042] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 11/21/2024 [ 231.452692] Workqueue: netns cleanup_net [ 231.452947] RIP: 0010:default_device_exit_batch+0x16c/0x3f0 [ 231.453326] Code: c0 0c f5 b3 e8 d5 db fe ff 48 85 c0 74 15 48 c7 c2 f8 fd ca b2 be 10 00 00 00 48 8d 7d c0 e8 7b 77 25 00 49 8b 86 28 01 00 00 <48> 8b 50 10 4c 8b 2a 4c 8d 62 f0 49 83 ed 10 4c 39 e0 0f 84 d6 00 [ 231.454294] RSP: 0018:ff75fc7c9bf9fd00 EFLAGS: 00010246 [ 231.454610] RAX: 0000000000000000 RBX: 0000000000000002 RCX: 61c8864680b583eb [ 231.455094] RDX: ff1fa9f71462d800 RSI: ff75fc7c9bf9fd38 RDI: 0000000030766564 [ 231.455686] RBP: ff75fc7c9bf9fd78 R08: 0000000000000000 R09: 0000000000000000 [ 231.456126] R10: 0000000000000001 R11: 0000000000000004 R12: ff1fa9f70088e340 [ 231.456621] R13: ff1fa9f70088e340 R14: ffffffffb3f50c20 R15: ff1fa9f7103e6340 [ 231.457161] FS: 0000000000000000(0000) GS:ff1faa6783a08000(0000) knlGS:0000000000000000 [ 231.457707] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 231.458031] CR2: 0000000000000010 CR3: 0000000179ab2006 CR4: 0000000000b73ef0 [ 231.458434] Call Trace: [ 231.458600] <TASK> [ 231.458777] ops_undo_list+0x100/0x220 [ 231.459015] cleanup_net+0x1b8/0x300 [ 231.459285] process_one_work+0x184/0x340

To fix it, move the VF namespace switching code from the NETDEV_REGISTER event handler to netvsc_open().

Cc: stable@vger.kernel.org Cc: cavery@redhat.com Fixes: 4c262801ea60 ("hv_netvsc: Fix VF namespace also in synthetic NIC NETDEV_REGISTER event") Signed-off-by: Haiyang Zhang haiyangz@microsoft.com --- v2: verified it's applicable to net, fixed cc list.

--- drivers/net/hyperv/netvsc_drv.c | 43 ++++++++++----------------------- 1 file changed, 13 insertions(+), 30 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c index 42d98e99566e..074ecc346108 100644 --- a/drivers/net/hyperv/netvsc_drv.c +++ b/drivers/net/hyperv/netvsc_drv.c @@ -135,6 +135,19 @@ static int netvsc_open(struct net_device *net) }

if (vf_netdev) { + if (!net_eq(dev_net(net), dev_net(vf_netdev))) { + ret = dev_change_net_namespace(vf_netdev, dev_net(net), + "eth%d"); + if (ret) + netdev_err(vf_netdev, + "Cannot move to same ns as %s: %d\n", + net->name, ret); + else + netdev_info(vf_netdev, + "Moved VF to namespace with: %s\n", + net->name); + } + /* Setting synthetic device up transparently sets * slave as up. If open fails, then slave will be * still be offline (and not used). @@ -2772,31 +2785,6 @@ static struct hv_driver netvsc_drv = { }, };

-/* Set VF's namespace same as the synthetic NIC */ -static void netvsc_event_set_vf_ns(struct net_device *ndev) -{ - struct net_device_context *ndev_ctx = netdev_priv(ndev); - struct net_device *vf_netdev; - int ret; - - vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev); - if (!vf_netdev) - return; - - if (!net_eq(dev_net(ndev), dev_net(vf_netdev))) { - ret = dev_change_net_namespace(vf_netdev, dev_net(ndev), - "eth%d"); - if (ret) - netdev_err(vf_netdev, - "Cannot move to same namespace as %s: %d\n", - ndev->name, ret); - else - netdev_info(vf_netdev, - "Moved VF to namespace with: %s\n", - ndev->name); - } -} - /* * On Hyper-V, every VF interface is matched with a corresponding * synthetic interface. The synthetic interface is presented first @@ -2809,11 +2797,6 @@ static int netvsc_netdev_event(struct notifier_block *this, struct net_device *event_dev = netdev_notifier_info_to_dev(ptr); int ret = 0;

- if (event_dev->netdev_ops == &device_ops && event == NETDEV_REGISTER) { - netvsc_event_set_vf_ns(event_dev); - return NOTIFY_DONE; - } - ret = check_dev_is_matching_vf(event_dev); if (ret != 0) return NOTIFY_DONE;