The UDC is not a suitable parent of the net device as the UDC can change or vanish during the lifecycle of the ethernet gadget. This can be illustrated with the following: mkdir -p /sys/kernel/config/usb_gadget/mygadget cd /sys/kernel/config/usb_gadget/mygadget mkdir -p configs/c.1/strings/0x409 echo "C1:Composite Device" > configs/c.1/strings/0x409/configuration mkdir -p functions/ecm.usb0 ln -s functions/ecm.usb0 configs/c.1/ echo "dummy_udc.0" > UDC rmmod dummy_hcd The 'rmmod' removes the UDC from the just created gadget, leaving the still existing net device with a no longer existing parent. Accessing the ethernet device with commands like: ip --details link show usb0 will result in a KASAN splat: ================================================================== BUG: KASAN: use-after-free in if_nlmsg_size+0x3e8/0x528 Read of size 4 at addr c5c84754 by task ip/357 CPU: 3 PID: 357 Comm: ip Not tainted 6.1.0-rc3-00013-gd14953726b24-dirty #324 Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x58/0x70 dump_stack_lvl from print_report+0x134/0x4d4 print_report from kasan_report+0x78/0x10c kasan_report from if_nlmsg_size+0x3e8/0x528 if_nlmsg_size from rtnl_getlink+0x2b4/0x4d0 rtnl_getlink from rtnetlink_rcv_msg+0x1f4/0x674 rtnetlink_rcv_msg from netlink_rcv_skb+0xb4/0x1f8 netlink_rcv_skb from netlink_unicast+0x294/0x478 netlink_unicast from netlink_sendmsg+0x328/0x640 netlink_sendmsg from ____sys_sendmsg+0x2a4/0x3b4 ____sys_sendmsg from ___sys_sendmsg+0xc8/0x12c ___sys_sendmsg from sys_sendmsg+0xa0/0x120 sys_sendmsg from ret_fast_syscall+0x0/0x1c Solve this by not setting the parent of the ethernet device. Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> --- drivers/usb/gadget/function/u_ether.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index e06022873df16..8f12f3f8f6eeb 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -798,7 +798,6 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g, net->max_mtu = GETHER_MAX_MTU_SIZE; dev->gadget = g; - SET_NETDEV_DEV(net, &g->dev); SET_NETDEV_DEVTYPE(net, &gadget_type); status = register_netdev(net); @@ -873,8 +872,6 @@ int gether_register_netdev(struct net_device *net) struct usb_gadget *g; int status; - if (!net->dev.parent) - return -EINVAL; dev = netdev_priv(net); g = dev->gadget; @@ -905,7 +902,6 @@ void gether_set_gadget(struct net_device *net, struct usb_gadget *g) dev = netdev_priv(net); dev->gadget = g; - SET_NETDEV_DEV(net, &g->dev); } EXPORT_SYMBOL_GPL(gether_set_gadget); -- 2.30.2
