RDMA/ipoib: Fix warning caused by destroying non-initial netns

In the Linux kernel, the following vulnerability has been resolved:

RDMA/ipoib: Fix warning caused by destroying non-initial netns

After the commit 5ce2dced8e95 ("RDMA/ipoib: Set rtnl_link_ops for ipoib

interfaces"), if the IPoIB device is moved to non-initial netns,

destroying that netns lets the device vanish instead of moving it back to

the initial netns, This is happening because default_device_exit() skips

the interfaces due to having rtnl_link_ops set.

Steps to reporoduce:

ip netns add foo

ip link set mlx5_ib0 netns foo

ip netns delete foo

WARNING: CPU: 1 PID: 704 at net/core/dev.c:11435 netdev_exit+0x3f/0x50

Modules linked in: xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT

nf_reject_ipv4 nft_compat nft_counter nft_chain_nat nf_nat nf_conntrack

nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink tun d

fuse

CPU: 1 PID: 704 Comm: kworker/u64:3 Tainted: G S W 5.13.0-rc1+ #1

Hardware name: Dell Inc. PowerEdge R630/02C2CP, BIOS 2.1.5 04/11/2016

Workqueue: netns cleanup_net

RIP: 0010:netdev_exit+0x3f/0x50

Code: 48 8b bb 30 01 00 00 e8 ef 81 b1 ff 48 81 fb c0 3a 54 a1 74 13 48

8b 83 90 00 00 00 48 81 c3 90 00 00 00 48 39 d8 75 02 5b c3 <0f> 0b 5b

c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 0f 1f 44 00

RSP: 0018:ffffb297079d7e08 EFLAGS: 00010206

RAX: ffff8eb542c00040 RBX: ffff8eb541333150 RCX: 000000008010000d

RDX: 000000008010000e RSI: 000000008010000d RDI: ffff8eb440042c00

RBP: ffffb297079d7e48 R08: 0000000000000001 R09: ffffffff9fdeac00

R10: ffff8eb5003be000 R11: 0000000000000001 R12: ffffffffa1545620

R13: ffffffffa1545628 R14: 0000000000000000 R15: ffffffffa1543b20

FS: 0000000000000000(0000) GS:ffff8ed37fa00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00005601b5f4c2e8 CR3: 0000001fc8c10002 CR4: 00000000003706e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

ops_exit_list.isra.9+0x36/0x70

cleanup_net+0x234/0x390

process_one_work+0x1cb/0x360

? process_one_work+0x360/0x360

worker_thread+0x30/0x370

? process_one_work+0x360/0x360

kthread+0x116/0x130

? kthread_park+0x80/0x80

ret_from_fork+0x22/0x30

To avoid the above warning and later on the kernel panic that could happen

on shutdown due to a NULL pointer dereference, make sure to set the

netns_refund flag that was introduced by commit 3a5ca857079e ("can: dev:

Move device back to init netns on owning netns delete") to properly

restore the IPoIB interfaces to the initial netns.