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Sascha Hauer
321b59870f
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@pengutronix.de> Link: https://lore.kernel.org/r/20221104131031.850850-2-s.hauer@pengutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.