scsi: megaraid_sas: Replace one-element array with flexible-array member in MR_PD_CFG_SEQ_NUM_SYNC

One-element arrays are deprecated, and we are replacing them with flexible
array members instead. So, replace one-element array with flexible-array
member in struct MR_PD_CFG_SEQ_NUM_SYNC and refactor the rest of the code
accordingly.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines
on memcpy() and help us make progress towards globally enabling
-fstrict-flex-arrays [0].

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Link: Link: https://reviews.llvm.org/D126864 [0]
Link: https://lore.kernel.org/r/78e9261591db072b67fcf49f0216d7046a67ca6d.1660592640.git.gustavoars@kernel.orgReviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/megaraid/megaraid_sas_base.c

@@ -5793,7 +5793,7 @@ megasas_setup_jbod_map(struct megasas_instance *instance)
 	u32 pd_seq_map_sz;
 
 	pd_seq_map_sz = sizeof(struct MR_PD_CFG_SEQ_NUM_SYNC) +
-		(sizeof(struct MR_PD_CFG_SEQ) * (MAX_PHYSICAL_DEVICES - 1));
+		(sizeof(struct MR_PD_CFG_SEQ) * MAX_PHYSICAL_DEVICES);
 
 	instance->use_seqnum_jbod_fp =
 		instance->support_seqnum_jbod_fp;
@@ -8046,7 +8046,7 @@ static void megasas_detach_one(struct pci_dev *pdev)
 		megasas_release_fusion(instance);
 		pd_seq_map_sz = sizeof(struct MR_PD_CFG_SEQ_NUM_SYNC) +
 				(sizeof(struct MR_PD_CFG_SEQ) *
-					(MAX_PHYSICAL_DEVICES - 1));
+					MAX_PHYSICAL_DEVICES);
 		for (i = 0; i < 2 ; i++) {
 			if (fusion->ld_map[i])
 				dma_free_coherent(&instance->pdev->dev,

drivers/scsi/megaraid/megaraid_sas_fusion.c

@@ -1310,7 +1310,7 @@ megasas_sync_pd_seq_num(struct megasas_instance *instance, bool pend) {
 
 	pd_sync = (void *)fusion->pd_seq_sync[(instance->pd_seq_map_id & 1)];
 	pd_seq_h = fusion->pd_seq_phys[(instance->pd_seq_map_id & 1)];
-	pd_seq_map_sz = struct_size(pd_sync, seq, MAX_PHYSICAL_DEVICES - 1);
+	pd_seq_map_sz = struct_size(pd_sync, seq, MAX_PHYSICAL_DEVICES);
 
 	cmd = megasas_get_cmd(instance);
 	if (!cmd) {

drivers/scsi/megaraid/megaraid_sas_fusion.h

@@ -1249,7 +1249,7 @@ struct MR_PD_CFG_SEQ {
 struct MR_PD_CFG_SEQ_NUM_SYNC {
 	__le32 size;
 	__le32 count;
-	struct MR_PD_CFG_SEQ seq[1];
+	struct MR_PD_CFG_SEQ seq[];
 } __packed;
 
 /* stream detection */