[Intel-wired-lan] [PATCH] i40e: Fix potential invalid access when MAC list is empty

[Zhen Ni]

list_first_entry() never returns NULL — if the list is empty, it still
returns a pointer to an invalid object, leading to potential invalid
memory access when dereferenced.

Fix this by checking list_empty() before calling list_first_entry(),
and only copying the MAC address when the list is not empty.

Fixes: e3219ce6a775 ("i40e: Add support for client interface for IWARP driver")
Signed-off-by: Zhen Ni <zhen...@easystack.cn>
---
 drivers/net/ethernet/intel/i40e/i40e_client.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_client.c 
b/drivers/net/ethernet/intel/i40e/i40e_client.c
index 5f1a405cbbf8..0a72157aee0e 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_client.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_client.c
@@ -359,12 +359,13 @@ static void i40e_client_add_instance(struct i40e_pf *pf)
        if (i40e_client_get_params(vsi, &cdev->lan_info.params))
                goto free_cdev;
 
-       mac = list_first_entry(&cdev->lan_info.netdev->dev_addrs.list,
-                              struct netdev_hw_addr, list);
-       if (mac)
+       if (!list_empty(&cdev->lan_info.netdev->dev_addrs.list)) {
+               mac = list_first_entry(&cdev->lan_info.netdev->dev_addrs.list,
+                                      struct netdev_hw_addr, list);
                ether_addr_copy(cdev->lan_info.lanmac, mac->addr);
-       else
+       } else {
                dev_err(&pf->pdev->dev, "MAC address list is empty!\n");
+       }
 
        pf->cinst = cdev;
 
-- 
2.20.1