nixge: fix mac address error handling again

The change to eth_hw_addr_set() caused gcc to correctly spot a
bug that was introduced in an earlier incorrect fix:

In file included from include/linux/etherdevice.h:21,
                 from drivers/net/ethernet/ni/nixge.c:7:
In function '__dev_addr_set',
    inlined from 'eth_hw_addr_set' at include/linux/etherdevice.h:319:2,
    inlined from 'nixge_probe' at drivers/net/ethernet/ni/nixge.c:1286:3:
include/linux/netdevice.h:4648:9: error: 'memcpy' reading 6 bytes from a region of size 0 [-Werror=stringop-overread]
 4648 |         memcpy(dev->dev_addr, addr, len);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

As nixge_get_nvmem_address() can return either NULL or an error
pointer, the NULL check is wrong, and we can end up reading from
ERR_PTR(-EOPNOTSUPP), which gcc knows to contain zero readable
bytes.

Make the function always return an error pointer again but fix
the check to match that.

Fixes: f3956ebb3bf0 ("ethernet: use eth_hw_addr_set() instead of ether_addr_copy()")
Fixes: abcd3d6fc640 ("net: nixge: Fix error path for obtaining mac address")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c
index cfeb762..07a00dd 100644 (file)
--- a/drivers/net/ethernet/ni/nixge.c
+++ b/drivers/net/ethernet/ni/nixge.c
@@ -1209,7 +1209,7 @@ static void *nixge_get_nvmem_address(struct device *dev)
 
        cell = nvmem_cell_get(dev, "address");
        if (IS_ERR(cell))
-               return NULL;
+               return cell;
 
        mac = nvmem_cell_read(cell, &cell_size);
        nvmem_cell_put(cell);
@@ -1282,7 +1282,7 @@ static int nixge_probe(struct platform_device *pdev)
        ndev->max_mtu = NIXGE_JUMBO_MTU;
 
        mac_addr = nixge_get_nvmem_address(&pdev->dev);
-       if (mac_addr && is_valid_ether_addr(mac_addr)) {
+       if (!IS_ERR(mac_addr) && is_valid_ether_addr(mac_addr)) {
                eth_hw_addr_set(ndev, mac_addr);
                kfree(mac_addr);
        } else {