[Qemu-devel] [6467] fix signed/unsigned overflows in SCSI disk (Rik van Riel)

[Anthony Liguori]

Revision: 6467
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6467
Author:   aliguori
Date:     2009-01-28 21:58:22 +0000 (Wed, 28 Jan 2009)

Log Message:
-----------
fix signed/unsigned overflows in SCSI disk (Rik van Riel)

Sector numbers can overflow on a virtual scsi disk of over 1TB
in size.  Qemu's bdrv_read expects an int64_t, so fix the overflow
by going to that data type.

On large disks, we clip the capacity to 2TB instead of returning
"capacity modulo 2TB".

Turn sector_count into an unsigned to prevent a signed/unsigned
overflow with SCSI transfers larger than 2TB.  We're unlikely to
ever hit this bug, but fixing it is just one line.

Signed-off-by: Rik van Riel <address@hidden>
Signed-off-by: Anthony Liguori <address@hidden>

Modified Paths:
--------------
    trunk/hw/scsi-disk.c

Modified: trunk/hw/scsi-disk.c
===================================================================
--- trunk/hw/scsi-disk.c        2009-01-28 17:16:56 UTC (rev 6466)
+++ trunk/hw/scsi-disk.c        2009-01-28 21:58:22 UTC (rev 6467)
@@ -47,11 +47,11 @@
 typedef struct SCSIRequest {
     SCSIDeviceState *dev;
     uint32_t tag;
-    /* ??? We should probably keep track of whether the data trasfer is
+    /* ??? We should probably keep track of whether the data transfer is
        a read or a write.  Currently we rely on the host getting it right.  */
     /* Both sector and sector_count are in terms of qemu 512 byte blocks.  */
-    int sector;
-    int sector_count;
+    uint64_t sector;
+    uint32_t sector_count;
     /* The amounnt of data in the buffer.  */
     int buf_len;
     uint8_t *dma_buf;
@@ -731,6 +731,9 @@
         /* Returned value is the address of the last sector.  */
         if (nb_sectors) {
             nb_sectors--;
+            /* Clip to 2TB, instead of returning capacity modulo 2TB. */
+            if (nb_sectors > UINT32_MAX)
+                nb_sectors = UINT32_MAX;
             outbuf[0] = (nb_sectors >> 24) & 0xff;
             outbuf[1] = (nb_sectors >> 16) & 0xff;
             outbuf[2] = (nb_sectors >> 8) & 0xff;