[PATCH 5.4 08/45] i40e: Fix potential invalid access when MAC list is empty

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhen Ni <zhen.ni@easystack.cn>

[ Upstream commit a556f06338e1d5a85af0e32ecb46e365547f92b9 ]

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 using list_first_entry_or_null instead of list_first_entry.

Fixes: e3219ce6a775 ("i40e: Add support for client interface for IWARP driver")
Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/intel/i40e/i40e_client.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_client.c b/drivers/net/ethernet/intel/i40e/i40e_client.c
index 10125b02d1543..b7c3625aec154 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_client.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_client.c
@@ -320,8 +320,8 @@ static void i40e_client_add_instance(struct i40e_pf *pf)
 		return;
 	}
 
-	mac = list_first_entry(&cdev->lan_info.netdev->dev_addrs.list,
-			       struct netdev_hw_addr, list);
+	mac = list_first_entry_or_null(&cdev->lan_info.netdev->dev_addrs.list,
+				       struct netdev_hw_addr, list);
 	if (mac)
 		ether_addr_copy(cdev->lan_info.lanmac, mac->addr);
 	else
-- 
2.50.1