On Tue, Jul 27, 2021 at 09:39:39PM -0400, 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. Yeah, I had the same fun. Maybe I should add a BUILD_BUG_ON() here to help illustrate the relationship? I did that in a few other places where the equalities weren't very clear. For example, change it to: + BUILD_BUG_ON(sizeof(evt_struct->iu.srp) != SRP_MAX_IU_LEN); + memset(&evt_struct->iu.srp, 0x00, sizeof(evt_struct->iu.srp)); srp_cmd = &evt_struct->iu.srp.cmd; - memset(srp_cmd, 0x00, SRP_MAX_IU_LEN); > > For good measure I copied Tyrel and Brian. > > Acked-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> For the moment, I'll leave the patch as-is unless you prefer having the BUILD_BUG_ON(). :) Thanks! -Kees > > > --- > > 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 -- Kees Cook
