In the Linux kernel, the following vulnerability has been resolved:
amt: Don't support cross-netns setup.
When a lower device is unregistered, amt_device_event() tries
to unregister its upper AMT device, but it has two problems.
1. amt_lookup_upper_dev() looks up an upper device in the
lower device's netns only
2. amt_device_event() unregisters a single upper device only
If AMT device is created on a lower device in another netns,
removing the lower device triggers the splat below and gets
stuck until all upper devices are removed. [0]
The cross-netns setup seems unintentional considering 1. and
the following points:
* amt_link_setup() sets dev->netns_immutable to true
* skb_scrub_packet() is not called in the fast path
* iproute2 binary fails to find cross-netns lower device via
link-netns:
# ip -n ns1 link add amt0 link-netns ns2 type amt dev veth1
Cannot find device "veth1"
Instead of supporting it properly and preparing for per-netns
netdev unreg, let's forbid cross-netns setup.
Note that the problem 2. needs a separate fix.
[0]:
WARNING: net/core/dev.c:12518 at unregister_netdevice_many_notify+0x1cce/0x2250, CPU#48: ip/2031
Modules linked in:
CPU: 48 UID: 0 PID: 2031 Comm: ip Not tainted 7.2.0-rc5+ #27 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
RIP: 0010:unregister_netdevice_many_notify (net/core/dev.c:12518)
Code: 89 ef e8 d5 52 ae fe e9 d0 f4 ff ff 48 8d 3d f9 3b 9c 02 48 c7 c6 c0 0b 63 84 ba ab 1f 00 00 67 48 0f b9 3a e9 65 ff ff ff 90 <0f> 0b 90 eb 81 48 8d 3d f6 3b 9c 02 48 c7 c6 c0 0b 63 84 ba e2 1f
RSP: 0018:ffffc90004abf160 EFLAGS: 00010212
RAX: ffff888104d38260 RBX: ffff88800b0911b8 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff85b9f880
RBP: ffffc90004abf2d0 R08: ffffffff85b9f887 R09: 1ffffffff0b73f10
R10: dffffc0000000000 R11: fffffbfff0b73f11 R12: ffff88800b091d08
R13: ffff88800b091178 R14: dffffc0000000000 R15: ffff88800b091000
FS: 00007f555b86c600(0000) GS:ffff8881942a0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000562107d489c0 CR3: 0000000109a40002 CR4: 0000000000372ef0
Call Trace:
Unknown