check blockno passed to idestart

1 files changed, 3 insertions, 1 deletions

diff --git a/ide.c b/ide.c
index 96216ea..ed5a572 100644
--- a/ide.c
+++ b/ide.c
@@ -48,7 +48,7 @@ void
 ideinit(void)
 {
   int i;
-
+  
   initlock(&idelock, "ide");
   picenable(IRQ_IDE);
   ioapicenable(IRQ_IDE, ncpu - 1);
@@ -73,6 +73,8 @@ idestart(struct buf *b)
 {
   if(b == 0)
     panic("idestart");
+  if(b->blockno >= FSSIZE)
+    panic("incorrect blockno");
   int sector_per_block =  BSIZE/SECTOR_SIZE;
   int sector = b->blockno * sector_per_block;