[PATCH v0] idb: Add rtnl_lock to avoid data race

From: Lin Ma
Date: Mon Aug 08 2022 - 04:12:09 EST


The commit c23d92b80e0b ("igb: Teardown SR-IOV before
unregister_netdev()") places the unregister_netdev() call after the
igb_disable_sriov() call to avoid functionality issue.

However, it introduces several race conditions when detaching a device.
For example, when .remove() is called, the below interleaving leads to
use-after-free.

(FREE from device detaching) | (USE from netdev core)
igb_remove | igb_ndo_get_vf_config
igb_disable_sriov | vf >= adapter->vfs_allocated_count?
kfree(adapter->vf_data) |
adapter->vfs_allocated_count = 0 |
| memcpy(... adapter->vf_data[vf]

In short, there are data races between read and write of
adapter->vfs_allocated_count. To fix this, we can add a new lock to
protect members in adapter object. However, we cau use the existing
rtnl_lock just as other drivers do. (See how dpaa2_eth_disconnect_mac is
protected in dpaa2_eth_remove function). This patch adopts similar
fixes.

Fixes: c23d92b80e0b ("igb: Teardown SR-IOV before unregister_netdev()")
Signed-off-by: Lin Ma <linma@xxxxxxxxxx>
---
drivers/net/ethernet/intel/igb/igb_main.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index d8b836a85cc3..e86ea4de05f8 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -3814,7 +3814,9 @@ static void igb_remove(struct pci_dev *pdev)
igb_release_hw_control(adapter);

#ifdef CONFIG_PCI_IOV
+ rtnl_lock();
igb_disable_sriov(pdev);
+ rtnl_unlock();
#endif

unregister_netdev(netdev);
--
2.36.1