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.