We are doing things like
nb_sectors /= (s->qdev.blocksize / BDRV_SECTOR_SIZE);
in the code here (e.g. in scsi_disk_emulate_mode_sense()), so if
the blocksize is smaller than BDRV_SECTOR_SIZE (=512), this crashes
with a division by 0 exception. Thus disallow block sizes of 256
bytes to avoid this situation.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1813
CVE: 2023-42467
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
hw/scsi/scsi-disk.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index e0d79c7966..477ee2bcd4 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1628,9 +1628,10 @@ static void scsi_disk_emulate_mode_select(SCSIDiskReq *r, uint8_t *inbuf)
* Since the existing code only checks/updates bits 8-15 of the block
* size, restrict ourselves to the same requirement for now to ensure
* that a block size set by a block descriptor and then read back by
- * a subsequent SCSI command will be the same
+ * a subsequent SCSI command will be the same. Also disallow a block
+ * size of 256 since we cannot handle anything below BDRV_SECTOR_SIZE.
*/
- if (bs && !(bs & ~0xff00) && bs != s->qdev.blocksize) {
+ if (bs && !(bs & ~0xfe00) && bs != s->qdev.blocksize) {
s->qdev.blocksize = bs;
trace_scsi_disk_mode_select_set_blocksize(s->qdev.blocksize);
}
--
2.41.0