Index: ata.c
===================================================================
--- ata.c	(revision 16556)
+++ ata.c	(working copy)
@@ -81,6 +81,7 @@
 #ifdef HAVE_LBA48
 static bool lba48 = false; /* set for 48 bit addressing */
 #endif
+unsigned long sector_count = 0;
 static long ata_stack[(DEFAULT_STACK_SIZE*3)/sizeof(long)];
 static const char ata_thread_name[] = "ata";
 static struct event_queue ata_queue;
@@ -277,6 +278,9 @@
     void* buf;
     long spinup_start;
 
+    if((start + incount) > sector_count)
+        return -6;
+
 #ifndef MAX_PHYS_SECTOR_SIZE
 #ifdef HAVE_MULTIVOLUME
     (void)drive; /* unused for now */
@@ -482,6 +486,9 @@
     int ret = 0;
     long spinup_start;
 
+    if((start + count) > sector_count)
+        panicf("Writing past end of disk\n");
+
 #ifndef MAX_PHYS_SECTOR_SIZE
 #ifdef HAVE_MULTIVOLUME
     (void)drive; /* unused for now */
@@ -621,6 +628,9 @@
     int rc = 0;
     int offset;
 
+    if((start + incount) > sector_count)
+        return -6;
+
 #ifdef HAVE_MULTIVOLUME
     (void)drive; /* unused for now */
 #endif
@@ -687,6 +697,9 @@
     int rc = 0;
     int offset;
 
+    if((start + count) > sector_count)
+        panicf("Writing past end of disk\n");
+
 #ifdef HAVE_MULTIVOLUME
     (void)drive; /* unused for now */
 #endif
@@ -1246,8 +1259,17 @@
             && identify_info[61] == 0x0FFF) /* (needs BigLBA addressing) */
         {
             lba48 = true; /* use BigLBA */
-        }
+            sector_count =  (unsigned long) identify_info[103] << 48 | 
+                            (unsigned long) identify_info[102] << 32 | 
+                            (unsigned long) identify_info[101] << 16 | 
+                            (unsigned long) identify_info[100];
+        }   
+        else
 #endif
+            sector_count =  (unsigned long) identify_info[61] << 16 | 
+                            (unsigned long) identify_info[60] ;
+
+
         rc = freeze_lock();
 
         if (rc)