ice: copy last block omitted in ice_get_module_eeprom()

ice_get_module_eeprom() is broken since commit e9c9692 ("ice:
Reimplement module reads used by ethtool") In this refactor,
ice_get_module_eeprom() reads the eeprom in blocks of size 8.
But the condition that should protect the buffer overflow
ignores the last block. The last block always contains zeros.

Bug uncovered by ethtool upstream commit 9538f384b535
("netlink: eeprom: Defer page requests to individual parsers")
After this commit, ethtool reads a block with length = 1;
to read the SFF-8024 identifier value.

unpatched driver:
$ ethtool -m enp65s0f0np0 offset 0x90 length 8
Offset          Values
------          ------
0x0090:         00 00 00 00 00 00 00 00
$ ethtool -m enp65s0f0np0 offset 0x90 length 12
Offset          Values
------          ------
0x0090:         00 00 01 a0 4d 65 6c 6c 00 00 00 00
$

$ ethtool -m enp65s0f0np0
Offset          Values
------          ------
0x0000:         11 06 06 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0010:         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0020:         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0030:         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0040:         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0050:         00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0060:         00 00 00 00 00 00 00 00 00 00 00 00 00 01 08 00
0x0070:         00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00

patched driver:
$ ethtool -m enp65s0f0np0 offset 0x90 length 8
Offset          Values
------          ------
0x0090:         00 00 01 a0 4d 65 6c 6c
$ ethtool -m enp65s0f0np0 offset 0x90 length 12
Offset          Values
------          ------
0x0090:         00 00 01 a0 4d 65 6c 6c 61 6e 6f 78
$ ethtool -m enp65s0f0np0
    Identifier                                : 0x11 (QSFP28)
    Extended identifier                       : 0x00
    Extended identifier description           : 1.5W max. Power consumption
    Extended identifier description           : No CDR in TX, No CDR in RX
    Extended identifier description           : High Power Class (> 3.5 W) not enabled
    Connector                                 : 0x23 (No separable connector)
    Transceiver codes                         : 0x88 0x00 0x00 0x00 0x00 0x00 0x00 0x00
    Transceiver type                          : 40G Ethernet: 40G Base-CR4
    Transceiver type                          : 25G Ethernet: 25G Base-CR CA-N
    Encoding                                  : 0x05 (64B/66B)
    BR, Nominal                               : 25500Mbps
    Rate identifier                           : 0x00
    Length (SMF,km)                           : 0km
    Length (OM3 50um)                         : 0m
    Length (OM2 50um)                         : 0m
    Length (OM1 62.5um)                       : 0m
    Length (Copper or Active cable)           : 1m
    Transmitter technology                    : 0xa0 (Copper cable unequalized)
    Attenuation at 2.5GHz                     : 4db
    Attenuation at 5.0GHz                     : 5db
    Attenuation at 7.0GHz                     : 7db
    Attenuation at 12.9GHz                    : 10db
    ........
    ....

Fixes: e9c9692 ("ice: Reimplement module reads used by ethtool")
Signed-off-by: Petr Oros <[email protected]>
Reviewed-by: Jesse Brandeburg <[email protected]>
Tested-by: Jesse Brandeburg <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: orosp

drivers/net/ethernet/intel/ice/ice_ethtool.c

@@ -4331,6 +4331,8 @@ ice_get_module_eeprom(struct net_device *netdev,
 		 * SFP modules only ever use page 0.
 		 */
 		if (page == 0 || !(data[0x2] & 0x4)) {
+			u32 copy_len;
+
 			/* If i2c bus is busy due to slow page change or
 			 * link management access, call can fail. This is normal.
 			 * So we retry this a few times.
@@ -4354,8 +4356,8 @@ ice_get_module_eeprom(struct net_device *netdev,
 			}
 
 			/* Make sure we have enough room for the new block */
-			if ((i + SFF_READ_BLOCK_SIZE) < ee->len)
-				memcpy(data + i, value, SFF_READ_BLOCK_SIZE);
+			copy_len = min_t(u32, SFF_READ_BLOCK_SIZE, ee->len - i);
+			memcpy(data + i, value, copy_len);
 		}
 	}
 	return 0;