CVE-2023-52574

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

team: fix null-ptr-deref when team device type is changed

Get a null-ptr-deref bug as follows with reproducer [1].

BUG: kernel NULL pointer dereference, address: 0000000000000228

...

RIP: 0010:vlan_dev_hard_header+0x35/0x140 [8021q]

...

Call Trace:

<TASK>

? __die+0x24/0x70

? page_fault_oops+0x82/0x150

? exc_page_fault+0x69/0x150

? asm_exc_page_fault+0x26/0x30

? vlan_dev_hard_header+0x35/0x140 [8021q]

? vlan_dev_hard_header+0x8e/0x140 [8021q]

neigh_connected_output+0xb2/0x100

ip6_finish_output2+0x1cb/0x520

? nf_hook_slow+0x43/0xc0

? ip6_mtu+0x46/0x80

ip6_finish_output+0x2a/0xb0

mld_sendpack+0x18f/0x250

mld_ifc_work+0x39/0x160

process_one_work+0x1e6/0x3f0

worker_thread+0x4d/0x2f0

? __pfx_worker_thread+0x10/0x10

kthread+0xe5/0x120

? __pfx_kthread+0x10/0x10

ret_from_fork+0x34/0x50

? __pfx_kthread+0x10/0x10

ret_from_fork_asm+0x1b/0x30

[1]

$ teamd -t team0 -d -c '{"runner": {"name": "loadbalance"}}'

$ ip link add name t-dummy type dummy

$ ip link add link t-dummy name t-dummy.100 type vlan id 100

$ ip link add name t-nlmon type nlmon

$ ip link set t-nlmon master team0

$ ip link set t-nlmon nomaster

$ ip link set t-dummy up

$ ip link set team0 up

$ ip link set t-dummy.100 down

$ ip link set t-dummy.100 master team0

When enslave a vlan device to team device and team device type is changed

from non-ether to ether, header_ops of team device is changed to

vlan_header_ops. That is incorrect and will trigger null-ptr-deref

for vlan->real_dev in vlan_dev_hard_header() because team device is not

a vlan device.

Cache eth_header_ops in team_setup(), then assign cached header_ops to

header_ops of team net device when its type is changed from non-ether

to ether to fix the bug.