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 Fixes: 4c262801ea60 ("hv_netvsc: Fix VF namespace also in synthetic NIC NETDEV_REGISTER event") Reported-by: Cathy Avery cavery@redhat.com Signed-off-by: Haiyang Zhang haiyangz@microsoft.com --- 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;
On Fri, 11 Jul 2025 13:57:10 -0700 Haiyang Zhang wrote:
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:
Are you saying that when netns is dismantled both devices are listed for moving back to default, but the netvsc_event_set_vf_ns() logic tries to undo the move / move the VF before the netns dismantle loop got to it?
This needs a better fix, moving on open is way too hacky. Perhaps we should start with reverting 4c262801ea60 and then trying to implement it in a more robust way?
-----Original Message----- From: Jakub Kicinski kuba@kernel.org Sent: Monday, July 14, 2025 9:29 PM To: Haiyang Zhang haiyangz@linux.microsoft.com Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; Haiyang Zhang haiyangz@microsoft.com; KY Srinivasan kys@microsoft.com; wei.liu@kernel.org; Dexuan Cui decui@microsoft.com; edumazet@google.com; pabeni@redhat.com; stephen@networkplumber.org; davem@davemloft.net; linux- kernel@vger.kernel.org; stable@vger.kernel.org Subject: [EXTERNAL] Re: [PATCH net] hv_netvsc: Switch VF namespace in netvsc_open instead
On Fri, 11 Jul 2025 13:57:10 -0700 Haiyang Zhang wrote:
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:
Are you saying that when netns is dismantled both devices are listed for moving back to default, but the netvsc_event_set_vf_ns() logic tries to undo the move / move the VF before the netns dismantle loop got to it?
netvsc_event_set_vf_ns() moves the VF to default ns before the netns dismantle loop got to it, and causes the Null prt error.
This needs a better fix, moving on open is way too hacky. Perhaps we should start with reverting 4c262801ea60 and then trying to implement it in a more robust way?
This patch reverts the 4c262801ea60, and moves the logic to netvsc_open().
I was thinking some other ways too... But seems I couldn't find a way to know it's in the for_each_netdev_safe loop, and to skip moving the VF in netvsc_event_set_vf_ns() this case.
Thanks, - Haiyang
linux-stable-mirror@lists.linaro.org
-
Haiyang Zhang -
Haiyang Zhang -
Jakub Kicinski