diff -rup qemu-0.9.0.orig/block.c qemu-0.9.0.new/block.c
--- qemu-0.9.0.orig/block.c	2007-02-05 18:01:54.000000000 -0500
+++ qemu-0.9.0.new/block.c	2008-02-23 10:35:58.000000000 -0500
@@ -120,6 +120,24 @@ void path_combine(char *dest, int dest_s
     }
 }
 
+static int bdrv_rw_badreq_sectors(BlockDriverState *bs,
+				int64_t sector_num, int nb_sectors)
+{
+    return
+	nb_sectors < 0 ||
+	nb_sectors > bs->total_sectors ||
+	sector_num > bs->total_sectors - nb_sectors;
+}
+
+static int bdrv_rw_badreq_bytes(BlockDriverState *bs,
+				  int64_t offset, int count)
+{
+    int64_t size = bs->total_sectors << SECTOR_BITS;
+    return
+	count < 0 ||
+	count > size ||
+	offset > size - count;
+}
 
 void bdrv_register(BlockDriver *bdrv)
 {
@@ -372,6 +390,7 @@ int bdrv_open2(BlockDriverState *bs, con
     }
     bs->drv = drv;
     bs->opaque = qemu_mallocz(drv->instance_size);
+    bs->total_sectors = 0; /* driver will set if it does not do getlength */
     if (bs->opaque == NULL && drv->instance_size > 0)
         return -1;
     /* Note: for compatibility, we open disk image files as RDWR, and
@@ -437,6 +456,7 @@ void bdrv_close(BlockDriverState *bs)
         bs->drv = NULL;
 
         /* call the change callback */
+	bs->total_sectors = 0;
         bs->media_changed = 1;
         if (bs->change_cb)
             bs->change_cb(bs->change_opaque);
@@ -502,6 +522,8 @@ int bdrv_read(BlockDriverState *bs, int6
     if (!drv)
         return -ENOMEDIUM;
 
+    if (bdrv_rw_badreq_sectors(bs, sector_num, nb_sectors))
+	return -EDOM;
     if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
             memcpy(buf, bs->boot_sector_data, 512);
         sector_num++;
@@ -539,6 +561,8 @@ int bdrv_write(BlockDriverState *bs, int
         return -ENOMEDIUM;
     if (bs->read_only)
         return -EACCES;
+    if (bdrv_rw_badreq_sectors(bs, sector_num, nb_sectors))
+	return -EDOM;
     if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
         memcpy(bs->boot_sector_data, buf, 512);   
     }
@@ -661,6 +685,8 @@ int bdrv_pread(BlockDriverState *bs, int
         return -ENOMEDIUM;
     if (!drv->bdrv_pread)
         return bdrv_pread_em(bs, offset, buf1, count1);
+    if (bdrv_rw_badreq_bytes(bs, offset, count1))
+	return -EDOM;
     return drv->bdrv_pread(bs, offset, buf1, count1);
 }
 
@@ -676,6 +702,8 @@ int bdrv_pwrite(BlockDriverState *bs, in
         return -ENOMEDIUM;
     if (!drv->bdrv_pwrite)
         return bdrv_pwrite_em(bs, offset, buf1, count1);
+    if (bdrv_rw_badreq_bytes(bs, offset, count1))
+	return -EDOM;
     return drv->bdrv_pwrite(bs, offset, buf1, count1);
 }
 
@@ -917,6 +945,8 @@ int bdrv_write_compressed(BlockDriverSta
         return -ENOMEDIUM;
     if (!drv->bdrv_write_compressed)
         return -ENOTSUP;
+    if (bdrv_rw_badreq_sectors(bs, sector_num, nb_sectors))
+	return -EDOM;
     return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
 }
     
@@ -1062,6 +1092,8 @@ BlockDriverAIOCB *bdrv_aio_read(BlockDri
 
     if (!drv)
         return NULL;
+    if (bdrv_rw_badreq_sectors(bs, sector_num, nb_sectors))
+        return NULL;
     
     /* XXX: we assume that nb_sectors == 0 is suppored by the async read */
     if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
@@ -1084,6 +1116,8 @@ BlockDriverAIOCB *bdrv_aio_write(BlockDr
         return NULL;
     if (bs->read_only)
         return NULL;
+    if (bdrv_rw_badreq_sectors(bs, sector_num, nb_sectors))
+	return NULL;
     if (sector_num == 0 && bs->boot_sector_enabled && nb_sectors > 0) {
         memcpy(bs->boot_sector_data, buf, 512);   
     }