net: dsa: make user ports return to init_net on netns deletion
As pointed out during review, currently the following set of commands crashes the kernel: $ ip netns add ns0 $ ip link set swp0 netns ns0 $ ip netns del ns0 WARNING: CPU: 1 PID: 27 at net/core/dev.c:10884 unregister_netdevice_many+0xaa4/0xaec Workqueue: netns cleanup_net pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : unregister_netdevice_many+0xaa4/0xaec lr : unregister_netdevice_many+0x700/0xaec Call trace: unregister_netdevice_many+0xaa4/0xaec default_device_exit_batch+0x294/0x340 ops_exit_list+0xac/0xc4 cleanup_net+0x2e4/0x544 process_one_work+0x4ec/0xb40 ---[ end trace 0000000000000000 ]--- unregister_netdevice: waiting for swp0 to become free. Usage count = 2 This is because since DSA user ports, since they started populating dev->rtnl_link_ops in the blamed commit, gained a different treatment from default_device_exit_net(), which thinks these interfaces can now be unregistered. They can't; so set netns_refund = true to restore the behavior prior to populating dev->rtnl_link_ops. Fixes: 95f510d0 ("net: dsa: allow the DSA master to be seen and changed through rtnetlink") Suggested-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://lore.kernel.org/r/20220921185428.1767001-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>
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