ice_get_module_eeprom() is broken since commit e9c9692c8a81 ("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: e9c9692c8a81 ("ice: Reimplement module reads used by ethtool")
Signed-off-by: Petr Oros <poros@redhat.com>
---
v2: memcpy unified calls
---
---
 drivers/net/ethernet/intel/ice/ice_ethtool.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
index b360bd8f15998b..1dc3f9fc74bdfb 100644
--- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
+++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
@@ -4293,6 +4293,7 @@ ice_get_module_eeprom(struct net_device *netdev,
 	bool is_sfp = false;
 	unsigned int i, j;
 	u16 offset = 0;
+	u32 copy_len;
 	u8 page = 0;
 	int status;
 
@@ -4354,8 +4355,9 @@ 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;
-- 
2.39.2

On 3/1/2023 9:14 AM, Petr Oros wrote:

>  drivers/net/ethernet/intel/ice/ice_ethtool.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> index b360bd8f15998b..1dc3f9fc74bdfb 100644
> --- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
> +++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
> @@ -4293,6 +4293,7 @@ ice_get_module_eeprom(struct net_device *netdev,
>  	bool is_sfp = false;
>  	unsigned int i, j;
>  	u16 offset = 0;
> +	u32 copy_len;

copy_len should only be declared in the "if" below so that it's only
declared in the context it is used.

>  	u8 page = 0;
>  	int status;
>  
> @@ -4354,8 +4355,9 @@ 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);

also this line can be unwrapped now.

> +			memcpy(data + i, value, copy_len);
>  		}
>  	}
>  	return 0;

I've tested this and it fixes the problem. Interestingly, the ethtool
application when compiled without netlink support parsed the output
correctly so caused a bit of confusion around this issue.

Thank you Petr!