Re: [PATCH 36/64] scsi: ibmvscsi: Avoid multi-field memset() overflow by aiming at srp

[Tyrel Datwyler]

On 7/27/21 6:39 PM, Martin K. Petersen wrote:
> 
> Kees,
> 
>> In preparation for FORTIFY_SOURCE performing compile-time and run-time
>> field bounds checking for memset(), avoid intentionally writing across
>> neighboring fields.
>>
>> Instead of writing beyond the end of evt_struct->iu.srp.cmd, target the
>> upper union (evt_struct->iu.srp) instead, as that's what is being wiped.
>>
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> 
> Orthogonal to your change, it wasn't immediately obvious to me that
> SRP_MAX_IU_LEN was the correct length to use for an srp_cmd. However, I
> traversed the nested unions and it does look OK.
> 
> For good measure I copied Tyrel and Brian.

LGTM

Acked-by: Tyrel Datwyler <tyreld@xxxxxxxxxxxxx>

> 
> Acked-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> 
>> ---
>>  drivers/scsi/ibmvscsi/ibmvscsi.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
>> index e6a3eaaa57d9..7e8beb42d2d3 100644
>> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
>> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
>> @@ -1055,8 +1055,8 @@ static int ibmvscsi_queuecommand_lck(struct scsi_cmnd *cmnd,
>>  		return SCSI_MLQUEUE_HOST_BUSY;
>>  
>>  	/* Set up the actual SRP IU */
>> +	memset(&evt_struct->iu.srp, 0x00, SRP_MAX_IU_LEN);
>>  	srp_cmd = &evt_struct->iu.srp.cmd;
>> -	memset(srp_cmd, 0x00, SRP_MAX_IU_LEN);
>>  	srp_cmd->opcode = SRP_CMD;
>>  	memcpy(srp_cmd->cdb, cmnd->cmnd, sizeof(srp_cmd->cdb));
>>  	int_to_scsilun(lun, &srp_cmd->lun);
>