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

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Date:   Mon,  8 Aug 2022 16:10:50 +0800
From:   Lin Ma <linma@....edu.cn>
To:     jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
        hawk@...nel.org, john.fastabend@...il.com,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Cc:     Lin Ma <linma@....edu.cn>
Subject: [PATCH v0] idb: Add rtnl_lock to avoid data race

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@....edu.cn>
---
 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