[PATCH 5 net] RDMA/core: fix UAF with ib_device_get_netdev()

[Denis Kirjanov <kirjanov@gmail.com>]

A call to ib_device_get_netdev may lead to a race condition
while accessing a netdevice instance since we don't hold
the rtnl lock while checking
the registration state:
	if (res && res->reg_state != NETREG_REGISTERED) {

v2: unlock rtnl on error path
v3: update remaining callers of ib_device_get_netdev
v4: don't call a cb with rtnl lock in ib_enum_roce_netdev
v5: put rtnl lock/unlock inside ib_device_get_netdev

Reported-by: syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com
Fixes: d41861942fc55 ("IB/core: Add generic function to extract IB speed from netdev")
Signed-off-by: Denis Kirjanov <dkirjanov@suse.de>
---
 drivers/infiniband/core/device.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 07cb6c5ffda0..7b379d3203d5 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -2240,14 +2240,17 @@ struct net_device *ib_device_get_netdev(struct ib_device *ib_dev,
 		spin_unlock(&pdata->netdev_lock);
 	}
 
+	rtnl_lock();
 	/*
 	 * If we are starting to unregister expedite things by preventing
 	 * propagation of an unregistering netdev.
 	 */
 	if (res && res->reg_state != NETREG_REGISTERED) {
+		rtnl_unlock();
 		dev_put(res);
 		return NULL;
 	}
+	rtnl_unlock();
 
 	return res;
 }
-- 
2.30.2