From: Antoine Tenart atenart@kernel.org
commit dde91ccfa25fd58f64c397d91b81a4b393100ffa upstream.
There is a short period between a net device starts to be unregistered and when it is actually gone. In that time frame ethtool operations could still be performed, which might end up in unwanted or undefined behaviours[1].
Do not allow ethtool operations after a net device starts its unregistration. This patch targets the netlink part as the ioctl one isn't affected: the reference to the net device is taken and the operation is executed within an rtnl lock section and the net device won't be found after unregister.
[1] For example adding Tx queues after unregister ends up in NULL pointer exceptions and UaFs, such as:
BUG: KASAN: use-after-free in kobject_get+0x14/0x90 Read of size 1 at addr ffff88801961248c by task ethtool/755
CPU: 0 PID: 755 Comm: ethtool Not tainted 5.15.0-rc6+ #778 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/014 Call Trace: dump_stack_lvl+0x57/0x72 print_address_description.constprop.0+0x1f/0x140 kasan_report.cold+0x7f/0x11b kobject_get+0x14/0x90 kobject_add_internal+0x3d1/0x450 kobject_init_and_add+0xba/0xf0 netdev_queue_update_kobjects+0xcf/0x200 netif_set_real_num_tx_queues+0xb4/0x310 veth_set_channels+0x1c3/0x550 ethnl_set_channels+0x524/0x610
Fixes: 041b1c5d4a53 ("ethtool: helper functions for netlink interface") Suggested-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Antoine Tenart atenart@kernel.org Link: https://lore.kernel.org/r/20211203101318.435618-1-atenart@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ethtool/netlink.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/ethtool/netlink.c +++ b/net/ethtool/netlink.c @@ -40,7 +40,8 @@ int ethnl_ops_begin(struct net_device *d if (dev->dev.parent) pm_runtime_get_sync(dev->dev.parent);
- if (!netif_device_present(dev)) { + if (!netif_device_present(dev) || + dev->reg_state == NETREG_UNREGISTERING) { ret = -ENODEV; goto err; }