Re: [PATCH 19/64] ip: Use struct_group() for memcpy() regions

[Bart Van Assche]

On 7/28/21 2:01 PM, Kees Cook wrote:
> On Wed, Jul 28, 2021 at 07:55:53AM +0200, Greg Kroah-Hartman wrote:
>>>  struct ethhdr {
>>> -	unsigned char	h_dest[ETH_ALEN];	/* destination eth addr	*/
>>> -	unsigned char	h_source[ETH_ALEN];	/* source ether addr	*/
>>> +	union {
>>> +		struct {
>>> +			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
>>> +			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
>>> +		};
>>> +		struct {
>>> +			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
>>> +			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
>>> +		} addrs;
>>
>> A union of the same fields in the same structure in the same way?
>>
>> Ah, because struct_group() can not be used here?  Still feels odd to see
>> in a userspace-visible header.
> 
> Yeah, there is some inconsistency here. I will clean this up for v2.
> 
> Is there a place we can put kernel-specific macros for use in UAPI
> headers? (I need to figure out where things like __kernel_size_t get
> defined...)

How about using two memset() calls to clear h_dest[] and h_source[]
instead of modifying the uapi header?

Thanks,

Bart.