Re: [PATCH rdma-rc] IB/core: fix a UAF for netdev in netdevice_event process

[Leon Romanovsky <leon@kernel.org>]

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@syzkaller.appspotmail.com
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
> ---
>  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()?

Thanks

>  
> -- 
> 2.25.1
>