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

On Mon, Oct 25, 2021 at 11:42:58AM +0800, Ziyang Xuan wrote:

quoted

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 <redacted>
---
 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

quoted

 
-- 
2.25.1

.