Subject: CVE-2021-47266: RDMA/ipoib: Fix warning caused by destroying non-initial netns

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2021-47266 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.4.73 with commit dc1d4c658b9c and fixed in 5.4.126 with commit 64f1fb6acc2a
	Issue introduced in 5.10 with commit 5ce2dced8e95 and fixed in 5.10.44 with commit 67cf4e447b5e
	Issue introduced in 5.10 with commit 5ce2dced8e95 and fixed in 5.12.11 with commit 0a672f7d89db
	Issue introduced in 5.10 with commit 5ce2dced8e95 and fixed in 5.13 with commit a3e74fb9247c
	Issue introduced in 5.8.17 with commit 938e97b946ec
	Issue introduced in 5.9.2 with commit 86e76dbea637

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47266
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/infiniband/ulp/ipoib/ipoib_netlink.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/64f1fb6acc2ab95982fc4334f351d7576c26f313
	https://git.kernel.org/stable/c/67cf4e447b5e5e9e94996cb6812ae2828e0e0e27
	https://git.kernel.org/stable/c/0a672f7d89db2da17ae02733ccc08458be72a6f8
	https://git.kernel.org/stable/c/a3e74fb9247cd530dca246699d5eb5a691884d32