Replace one-element array with flexible-array member

Hi!

This series aims to replace one-element arrays with flexible-array members in drivers/scsi/hptiop.h

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=3 [1].

Gustavo A. R. Silva (2):
scsi: hptiop: Replace one-element array with flexible-array member
scsi: hptiop: Use struct_size() helper in code related to struct
hpt_iop_request_scsi_command

 drivers/scsi/hptiop.c | 9 +++------
 drivers/scsi/hptiop.h | 2 +-
 2 files changed, 4 insertions(+), 7 deletions(-)

2.34.1

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 hpt_iop_request_scsi_command and refactor the rest of the code, accordingly.

The following pieces of code suggest that the one element of array sg_list in struct hpt_iop_request_scsi_command is not taken into account when calculating the total size for both struct hpt_iop_request_scsi_command and the maximum number of elements sg_list will contain:

1047 req->header.size = cpu_to_le32(
1048 sizeof(struct hpt_iop_request_scsi_command)
1049 - sizeof(struct hpt_iopsg)
1050 + sg_count * sizeof(struct hpt_iopsg));

1400 req_size = sizeof(struct hpt_iop_request_scsi_command) 1401 + sizeof(struct hpt_iopsg) * (hba->max_sg_descriptors - 1);

So it's safe to replace the one-element array with a flexible-array member and update the code above, accordingly: now we don't need to subtract sizeof(struct hpt_iopsg) from sizeof(struct hpt_iop_request_scsi_command) because this is implicitly done by the flex-array transformation.

---
 drivers/scsi/hptiop.c | 3 +--
 drivers/scsi/hptiop.h | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

index f18b770626e6..cfc6546e35a6 100644
@@ -1046,7 +1046,6 @@ static int hptiop_queuecommand_lck(struct scsi_cmnd *scp)
 	req->lun = scp->device->lun;
 	req->header.size = cpu_to_le32(
 				sizeof(struct hpt_iop_request_scsi_command)
-				 - sizeof(struct hpt_iopsg)
 				 + sg_count * sizeof(struct hpt_iopsg));
 
 	memcpy(req->cdb, scp->cmnd, sizeof(req->cdb));

@@ -1398,7 +1397,7 @@ static int hptiop_probe(struct pci_dev *pcidev, const struct pci_device_id *id)
 	host->max_cmd_len = 16;
 
 	req_size = sizeof(struct hpt_iop_request_scsi_command)
-		+ sizeof(struct hpt_iopsg) * (hba->max_sg_descriptors - 1);
+		+ sizeof(struct hpt_iopsg) * hba->max_sg_descriptors;
 	if ((req_size & 0x1f) != 0)
 		req_size = (req_size + 0x1f) & ~0x1f;
 

index 363d5a16243f..ef2f2aca598c 100644
@@ -228,7 +228,7 @@ struct hpt_iop_request_scsi_command {
 	u8     pad1;
 	u8     cdb[16];
 	__le32 dataxfer_length;
-	struct hpt_iopsg sg_list[1];
+	struct hpt_iopsg sg_list[];
 };
 
 struct hpt_iop_request_ioctl_command {

2.34.1

Accidentally merge line above ("1401" should start a new line).

The only binary output change I see is from the line numbers changing from the patch, as the argument to __might_sleep() is adjusted:

...

│       call   d1 <hptiop_reset+0x74>
│   R_X86_64_PLT32      __x86_indirect_thunk_rax-0x4
│ -     mov    $0x434,%esi
│ +     mov    $0x433,%esi
│       mov    $0x0,%rdi
│   R_X86_64_32S        .rodata.str1.1
│       call   e2 <hptiop_reset+0x85>
│   R_X86_64_PLT32      __might_sleep-0x4

...

So this looks good!

Kees Cook

Prefer struct_size() over open-coded versions of idiom:

sizeof(struct-with-flex-array) + sizeof(typeof-flex-array-elements) * count

where count is the max number of items the flexible array is supposed to contain.

---
 drivers/scsi/hptiop.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

index cfc6546e35a6..7e8903718245 100644
@@ -1044,9 +1044,7 @@ static int hptiop_queuecommand_lck(struct scsi_cmnd *scp)
 	req->channel = scp->device->channel;
 	req->target = scp->device->id;
 	req->lun = scp->device->lun;
-	req->header.size = cpu_to_le32(
-				sizeof(struct hpt_iop_request_scsi_command)
-				 + sg_count * sizeof(struct hpt_iopsg));
+	req->header.size = cpu_to_le32(struct_size(req, sg_list, sg_count));
 
 	memcpy(req->cdb, scp->cmnd, sizeof(req->cdb));
 	hba->ops->post_req(hba, _req);

@@ -1396,8 +1394,8 @@ static int hptiop_probe(struct pci_dev *pcidev, const struct pci_device_id *id)
 	host->cmd_per_lun = le32_to_cpu(iop_config.max_requests);
 	host->max_cmd_len = 16;
 
-	req_size = sizeof(struct hpt_iop_request_scsi_command)
-		+ sizeof(struct hpt_iopsg) * hba->max_sg_descriptors;
+	req_size = struct_size((struct hpt_iop_request_scsi_command *)0,
+			       sg_list, hba->max_sg_descriptors);
 	if ((req_size & 0x1f) != 0)
 		req_size = (req_size + 0x1f) & ~0x1f;
 

2.34.1

Looks correct; thanks!

Kees Cook

Gustavo,

Applied to 6.1/scsi-staging, thanks!

Martin K. Petersen	Oracle Linux Engineering