Re: [PATCH] scsi: megaraid_sas: struct MR_HOST_DEVICE_LIST: Replace 1-element array with flexible array

[James Bottomley]

On Thu, 2024-07-11 at 08:58 -0700, Kees Cook wrote:
> Replace the deprecated[1] use of a 1-element array in
> struct MR_HOST_DEVICE_LIST with a modern flexible array.
> 
> One binary difference appears in megasas_host_device_list_query():
> 
>         struct MR_HOST_DEVICE_LIST *ci;
>         ...
>         ci = instance->host_device_list_buf;
>         ...
>         memset(ci, 0, sizeof(*ci));
> 
> The memset() clears only the non-flexible array fields. Looking at
> the rest of the function, this appears to be fine: firmware is using
> this region to communicate with the kernel, so it likely never made
> sense to clear the first MR_HOST_DEVICE_LIST_ENTRY.

That's not necessarily a safe assumption: older qlogic for instance
uses zeroing an entry to stop the card mailbox processing.  Looking at
the driver, I think you're right: it's only used for card to host
communication, so clearing it is irrelevant, but it could be relevant
if it were also used for host to card communication.

Regards,

James