[PATCH 1/3][next] scsi: smartpqi: Replace one-element array with flexible-array member

["Gustavo A. R. Silva" <gustavoars@kernel.org>]

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_DRV_RAID_MAP and refactor the the rest of the code
accordingly.

It seems that the addition of sizeof(struct report_log_lun) in all the
places that are modified by this patch is due to the fact that
the one-element array struct report_log_lun lun_entries[1]; always
contributes to the size of the containing structure struct
report_log_lun_list.

Notice that at line 1267 while allocating memory for an instance of
struct report_log_lun_list, some _extra_ space seems to be allocated
for one element of type struct report_log_lun, which is the type of
the elements in array lun_entries:

 1267         internal_logdev_list = kmalloc(logdev_data_length +
 1268                 sizeof(struct report_log_lun), GFP_KERNEL);

However, at line 1275 just logdev_data_length bytes are copied into
internal_logdev_list (remember that we allocated space for logdev_data_length +
sizeof(struct report_log_lun) bytes at line 1267), and then exactly
sizeof(struct report_log_lun) bytes are being zeroing out at line 1276.

 1275         memcpy(internal_logdev_list, logdev_data, logdev_data_length);
 1276         memset((u8 *)internal_logdev_list + logdev_data_length, 0,
 1277                 sizeof(struct report_log_lun));

All the above makes think that it's just fine if we transform array
lun_entries into a flexible-array member and just don't allocate
that extra sizeof(struct report_log_lun) bytes of space. With this
we can remove that memset() call and we also need to modify the code
that updates the total length (internal_logdev_list->header.list_length)
of array lun_entries at line 1278:

 1278         put_unaligned_be32(logdev_list_length +
 1279                 sizeof(struct report_log_lun),
 1280                 &internal_logdev_list->header.list_length);

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/204
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
And of course, it'd be great if maintainers can confirm what I described
in the changelog text. :)

 drivers/scsi/smartpqi/smartpqi.h      |  2 +-
 drivers/scsi/smartpqi/smartpqi_init.c | 10 +++-------
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/smartpqi/smartpqi.h b/drivers/scsi/smartpqi/smartpqi.h
index e550b12e525a..d1756c9d1112 100644
--- a/drivers/scsi/smartpqi/smartpqi.h
+++ b/drivers/scsi/smartpqi/smartpqi.h
@@ -954,7 +954,7 @@ struct report_log_lun {
 
 struct report_log_lun_list {
 	struct report_lun_header header;
-	struct report_log_lun lun_entries[1];
+	struct report_log_lun lun_entries[];
 };
 
 struct report_phys_lun_8byte_wwid {
diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c
index b971fbe3b3a1..544cd18a90d7 100644
--- a/drivers/scsi/smartpqi/smartpqi_init.c
+++ b/drivers/scsi/smartpqi/smartpqi_init.c
@@ -1264,8 +1264,7 @@ static int pqi_get_device_lists(struct pqi_ctrl_info *ctrl_info,
 	logdev_data_length = sizeof(struct report_lun_header) +
 		logdev_list_length;
 
-	internal_logdev_list = kmalloc(logdev_data_length +
-		sizeof(struct report_log_lun), GFP_KERNEL);
+	internal_logdev_list = kmalloc(logdev_data_length, GFP_KERNEL);
 	if (!internal_logdev_list) {
 		kfree(*logdev_list);
 		*logdev_list = NULL;
@@ -1273,11 +1272,8 @@ static int pqi_get_device_lists(struct pqi_ctrl_info *ctrl_info,
 	}
 
 	memcpy(internal_logdev_list, logdev_data, logdev_data_length);
-	memset((u8 *)internal_logdev_list + logdev_data_length, 0,
-		sizeof(struct report_log_lun));
-	put_unaligned_be32(logdev_list_length +
-		sizeof(struct report_log_lun),
-		&internal_logdev_list->header.list_length);
+	put_unaligned_be32(logdev_list_length,
+			   &internal_logdev_list->header.list_length);
 
 	kfree(*logdev_list);
 	*logdev_list = internal_logdev_list;
-- 
2.34.1