scsi: lpfc: Fix ras_log via debugfs

/sys/kernel/debug/lpfc/fn0/ras_log always shows the same ras_log even if
there are link bounce events triggered via issue_lip

Dynamic FW logging had logic that prematurely breaks from the buffer
filling loop.

Fix the check for buffer overrun by looking before copying and restricting
copy length to the remaining buffer.  When copying, ensure space for NULL
character is left in the buffer.  While in the routine - ensure the buffer
is cleared before adding elements.

Link: https://lore.kernel.org/r/20191218235808.31922-6-jsmart2021@gmail.comSigned-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_debugfs.c

@@ -2085,6 +2085,8 @@ static int lpfc_debugfs_ras_log_data(struct lpfc_hba *phba,
 	int copied = 0;
 	struct lpfc_dmabuf *dmabuf, *next;
 
+	memset(buffer, 0, size);
+
 	spin_lock_irq(&phba->hbalock);
 	if (phba->ras_fwlog.state != ACTIVE) {
 		spin_unlock_irq(&phba->hbalock);
@@ -2094,10 +2096,15 @@ static int lpfc_debugfs_ras_log_data(struct lpfc_hba *phba,
 
 	list_for_each_entry_safe(dmabuf, next,
 				 &phba->ras_fwlog.fwlog_buff_list, list) {
+		/* Check if copying will go over size and a '\0' char */
+		if ((copied + LPFC_RAS_MAX_ENTRY_SIZE) >= (size - 1)) {
+			memcpy(buffer + copied, dmabuf->virt,
+			       size - copied - 1);
+			copied += size - copied - 1;
+			break;
+		}
 		memcpy(buffer + copied, dmabuf->virt, LPFC_RAS_MAX_ENTRY_SIZE);
 		copied += LPFC_RAS_MAX_ENTRY_SIZE;
-		if (size > copied)
-			break;
 	}
 	return copied;
 }