> On Mon, Oct 25, 2021 at 11:42:58AM +0800, Ziyang Xuan wrote:
>> When a vlan netdev enter netdevice_event process although it is not a
>> roce netdev, it will be passed to netdevice_event_work_handler() to
>> process. In order to hold the netdev of netdevice_event after
>> netdevice_event() return, call dev_hold() to hold the netdev in
>> netdevice_queue_work(). But that did not consider the real_dev of a vlan
>> netdev, the real_dev can be freed within netdevice_event_work_handler()
>> be scheduled. It would trigger the UAF problem for the real_dev like
>> following:
>>
>> ==================================================================
>> BUG: KASAN: use-after-free in vlan_dev_real_dev+0xf9/0x120
>> Read of size 4 at addr ffff88801648a0c4 by task kworker/u8:0/8
>> Workqueue: gid-cache-wq netdevice_event_work_handler
>> Call Trace:
>> dump_stack_lvl+0xcd/0x134
>> print_address_description.constprop.0.cold+0x93/0x334
>> kasan_report.cold+0x83/0xdf
>> vlan_dev_real_dev+0xf9/0x120
>> is_eth_port_of_netdev_filter.part.0+0xb1/0x2c0
>> is_eth_port_of_netdev_filter+0x28/0x40
>> ib_enum_roce_netdev+0x1a3/0x300
>> ib_enum_all_roce_netdevs+0xc7/0x140
>> netdevice_event_work_handler+0x9d/0x210
>> ...
>>
>> Allocated by task 9289:
>> kasan_save_stack+0x1b/0x40
>> __kasan_kmalloc+0x9b/0xd0
>> __kmalloc_node+0x20a/0x330
>> kvmalloc_node+0x61/0xf0
>> alloc_netdev_mqs+0x9d/0x1140
>> rtnl_create_link+0x955/0xb70
>> __rtnl_newlink+0xe10/0x15b0
>> rtnl_newlink+0x64/0xa0
>> ...
>>
>> Freed by task 9288:
>> kasan_save_stack+0x1b/0x40
>> kasan_set_track+0x1c/0x30
>> kasan_set_free_info+0x20/0x30
>> __kasan_slab_free+0xfc/0x130
>> slab_free_freelist_hook+0xdd/0x240
>> kfree+0xe4/0x690
>> kvfree+0x42/0x50
>> device_release+0x9f/0x240
>> kobject_put+0x1c8/0x530
>> put_device+0x1b/0x30
>> free_netdev+0x370/0x540
>> ppp_destroy_interface+0x313/0x3d0
>> ppp_release+0x1bf/0x240
>> ...
>>
>> Hold the real_dev for a vlan netdev in netdevice_event_work_handler()
>> to fix the UAF problem.
>>
>> Fixes: 238fdf48f2b5 ("IB/core: Add RoCE table bonding support")
>> Reported-by: syzbot+e4df4e1389e28972e955@xxxxxxxxxxxxxxxxxxxxxxxxx
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
>> ---
>> drivers/infiniband/core/roce_gid_mgmt.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/infiniband/core/roce_gid_mgmt.c b/drivers/infiniband/core/roce_gid_mgmt.c
>> index 68197e576433..063dbe72b7c2 100644
>> --- a/drivers/infiniband/core/roce_gid_mgmt.c
>> +++ b/drivers/infiniband/core/roce_gid_mgmt.c
>> @@ -621,6 +621,7 @@ static void netdevice_event_work_handler(struct work_struct *_work)
>> {
>> struct netdev_event_work *work =
>> container_of(_work, struct netdev_event_work, work);
>> + struct net_device *real_dev;
>> unsigned int i;
>>
>> for (i = 0; i < ARRAY_SIZE(work->cmds) && work->cmds[i].cb; i++) {
>> @@ -628,6 +629,12 @@ static void netdevice_event_work_handler(struct work_struct *_work)
>> work->cmds[i].filter_ndev,
>> work->cmds[i].cb,
>> work->cmds[i].ndev);
>> + real_dev = rdma_vlan_dev_real_dev(work->cmds[i].ndev);
>> + if (real_dev)
>> + dev_put(real_dev);
>> + real_dev = rdma_vlan_dev_real_dev(work->cmds[i].filter_ndev);
>> + if (real_dev)
>> + dev_put(real_dev);
>> dev_put(work->cmds[i].ndev);
>> dev_put(work->cmds[i].filter_ndev);
>> }
>> @@ -638,9 +645,10 @@ static void netdevice_event_work_handler(struct work_struct *_work)
>> static int netdevice_queue_work(struct netdev_event_work_cmd *cmds,
>> struct net_device *ndev)
>> {
>> - unsigned int i;
>> struct netdev_event_work *ndev_work =
>> kmalloc(sizeof(*ndev_work), GFP_KERNEL);
>> + struct net_device *real_dev;
>> + unsigned int i;
>>
>> if (!ndev_work)
>> return NOTIFY_DONE;
>> @@ -653,6 +661,12 @@ static int netdevice_queue_work(struct netdev_event_work_cmd *cmds,
>> ndev_work->cmds[i].filter_ndev = ndev;
>> dev_hold(ndev_work->cmds[i].ndev);
>> dev_hold(ndev_work->cmds[i].filter_ndev);
>> + real_dev = rdma_vlan_dev_real_dev(ndev_work->cmds[i].ndev);
>> + if (real_dev)
>> + dev_hold(real_dev);
>> + real_dev = rdma_vlan_dev_real_dev(ndev_work->cmds[i].filter_ndev);
>> + if (real_dev)
>> + dev_hold(real_dev);
>> }
>> INIT_WORK(&ndev_work->work, netdevice_event_work_handler);
>
> Probably, this is the right change, but I don't know well enough that
> part of code. What prevents from "real_dev" to disappear right after
> your call to rdma_vlan_dev_real_dev()?
>
It is known that free the net_device until its dev_refcnt is one. The
detail realization see netdev_run_todo().The real_dev's dev_refcnt of
a vlan net_device will reach one after unregister_netdevice(&real_dev)
and unregister_vlan_dev(&vlan_ndev, ...) but the dev_refcnt of the vlan
net_device is bigger than one because netdevice_queue_work() will hold
the vlan net_device. So my solution is hold the real_dev too in
netdevice_queue_work().
> Thanks
>
>>
>> --
>> 2.25.1
>>
> .
>
