niu: fix missing checks of niu_pci_eeprom_read

niu_pci_eeprom_read() may fail, so we should check its return value
before using the read data.
Signed-off-by: NKangjie Lu <kjlu@umn.edu>
Acked-by: NShannon Nelson <shannon.lee.nelson@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/niu.c

@@ -8100,6 +8100,8 @@ static int niu_pci_vpd_scan_props(struct niu *np, u32 start, u32 end)
 		start += 3;
 
 		prop_len = niu_pci_eeprom_read(np, start + 4);
+		if (prop_len < 0)
+			return prop_len;
 		err = niu_pci_vpd_get_propname(np, start + 5, namebuf, 64);
 		if (err < 0)
 			return err;
@@ -8144,8 +8146,12 @@ static int niu_pci_vpd_scan_props(struct niu *np, u32 start, u32 end)
 			netif_printk(np, probe, KERN_DEBUG, np->dev,
 				     "VPD_SCAN: Reading in property [%s] len[%d]\n",
 				     namebuf, prop_len);
-			for (i = 0; i < prop_len; i++)
-				*prop_buf++ = niu_pci_eeprom_read(np, off + i);
+			for (i = 0; i < prop_len; i++) {
+				err = niu_pci_eeprom_read(np, off + i);
+				if (err >= 0)
+					*prop_buf = err;
+				++prop_buf;
+			}
 		}
 
 		start += len;