RE: [PATCH 5.10.y] e1000e: fix EEPROM length types for overflow checks

["Farber, Eliav" <farbere@amazon.com>]

> On Wed, Sep 10, 2025 at 05:31:38PM +0000, Eliav Farber wrote:
>> Fix a compilation failure when warnings are treated as errors:
>>
>> drivers/net/ethernet/intel/e1000e/ethtool.c: In function ‘e1000_set_eeprom’:
>> ./include/linux/overflow.h:71:15: error: comparison of distinct pointer types lacks a cast [-Werror]
>>    71 |  (void) (&__a == __d);   \
>>       |               ^~
>> drivers/net/ethernet/intel/e1000e/ethtool.c:582:6: note: in expansion of macro ‘check_add_overflow’
>>   582 |  if (check_add_overflow(eeprom->offset, eeprom->len, &total_len) ||
>>       |      ^~~~~~~~~~~~~~~~~~
>>
>> To fix this, change total_len and max_len from size_t to u32 in 
>> e1000_set_eeprom().
>> The check_add_overflow() helper requires that the first two operands 
>> and the pointer to the result (third operand) all have the same type.
>> On 64-bit builds, using size_t caused a mismatch with the u32 fields
>> eeprom->offset and eeprom->len, leading to type check failures.
>>
>> Fixes: ce8829d3d44b ("e1000e: fix heap overflow in e1000_set_eeprom")
>> Signed-off-by: Eliav Farber <farbere@amazon.com>
>> ---
>>  drivers/net/ethernet/intel/e1000e/ethtool.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/e1000e/ethtool.c 
>> b/drivers/net/ethernet/intel/e1000e/ethtool.c
>> index 4aca854783e2..584378291f3f 100644
>> --- a/drivers/net/ethernet/intel/e1000e/ethtool.c
>> +++ b/drivers/net/ethernet/intel/e1000e/ethtool.c
>> @@ -559,7 +559,7 @@ static int e1000_set_eeprom(struct net_device 
>> *netdev,  {
>>       struct e1000_adapter *adapter = netdev_priv(netdev);
>>       struct e1000_hw *hw = &adapter->hw;
>> -     size_t total_len, max_len;
>> +     u32 total_len, max_len;
>>       u16 *eeprom_buff;
>>       int ret_val = 0;
>>       int first_word;
>> --
>> 2.47.3
>>
>
> Why is this not needed in Linus's tree?
Kernel 5.10.243 enforces the same type, but this enforcement is
absent from 5.15.192 and later:
/*
 * For simplicity and code hygiene, the fallback code below insists on
 * a, b and *d having the same type (similar to the min() and max()
 * macros), whereas gcc's type-generic overflow checkers accept
 * different types. Hence we don't just make check_add_overflow an
 * alias for __builtin_add_overflow, but add type checks similar to
 * below.
 */
#define check_add_overflow(a, b, d) __must_check_overflow(({	\
 
> Also, why is it not cc: stable@vger.kernel.org?
Added to cc.

---
Regards, Eliav