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    Subject[PATCH net v3] team: fix null-ptr-deref when team device type is changed
    Date
    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@gmail.com>
    Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
    ---
    v3:
    - Export eth_header_ops to fix modpost error.
    v2:
    - Just modify header_ops to eth_header_ops not use ether_setup().
    ---
    drivers/net/team/team.c | 5 ++++-
    net/ethernet/eth.c | 1 +
    2 files changed, 5 insertions(+), 1 deletion(-)

    diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
    index d3dc22509ea5..12fb5f4cff06 100644
    --- a/drivers/net/team/team.c
    +++ b/drivers/net/team/team.c
    @@ -2127,7 +2127,10 @@ static const struct ethtool_ops team_ethtool_ops = {
    static void team_setup_by_port(struct net_device *dev,
    struct net_device *port_dev)
    {
    - dev->header_ops = port_dev->header_ops;
    + if (port_dev->type == ARPHRD_ETHER)
    + dev->header_ops = &eth_header_ops;
    + else
    + dev->header_ops = port_dev->header_ops;
    dev->type = port_dev->type;
    dev->hard_header_len = port_dev->hard_header_len;
    dev->needed_headroom = port_dev->needed_headroom;
    diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
    index 2edc8b796a4e..157833509adb 100644
    --- a/net/ethernet/eth.c
    +++ b/net/ethernet/eth.c
    @@ -347,6 +347,7 @@ const struct header_ops eth_header_ops ____cacheline_aligned = {
    .cache_update = eth_header_cache_update,
    .parse_protocol = eth_header_parse_protocol,
    };
    +EXPORT_SYMBOL(eth_header_ops);

    /**
    * ether_setup - setup Ethernet network device
    --
    2.25.1
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