Re: [PATCH net v3] team: fix null-ptr-deref when team device type is changed

[Ziyang Xuan (William)]

> On Tue, 2023-09-05 at 16:10 +0800, Ziyang Xuan wrote:
>> 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.
>>
>> Assign eth_header_ops to header_ops of team device when its type is changed
>> from non-ether to ether to fix the bug.
>>
>> Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
>> Suggested-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
> 
> I'm sorry to note that this submission does not fit our process:
> 
> https://elixir.bootlin.com/linux/latest/source/Documentation/process/maintainer-netdev.rst#L353
> 
> this specific kind of process violations tend to make reviewers quite
> unhappy, please be more careful.
> 
Sorry for the inconvenience caused to everyone. It's my fault. I will improve.

> Regards,
> 
> Paolo
> 
> .
>