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

Martin K. Petersen
2021-07-28T01:40:37Z

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@chromium.org>

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.

Acked-by: Martin K. Petersen <martin.petersen@oracle.com>

> ---
> 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);

--
Martin K. Petersen Oracle Linux Engineering