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

[Paolo Abeni]

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.

Regards,

Paolo