netdev - Re: [PATCH net v5] team: fix null-ptr-deref when team device type is changed

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Date: Mon, 18 Sep 2023 14:50:54 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Ziyang Xuan <william.xuanziyang@...wei.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org, liuhangbin@...il.com
Subject: Re: [PATCH net v5] team: fix null-ptr-deref when team device type is
 changed

Mon, Sep 18, 2023 at 02:30:11PM CEST, william.xuanziyang@...wei.com 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.
>
>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.
>
>Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
>Suggested-by: Hangbin Liu <liuhangbin@...il.com>
>Reviewed-by: Hangbin Liu <liuhangbin@...il.com>
>Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>

Reviewed-by: Jiri Pirko <jiri@...dia.com>