iscsi: Avoid potential for get_status overflow

Detected by Coverity: Multiplying two 32-bit int and assigning
the result to a 64-bit number is a risk of overflow.  Prior to
the conversion to byte-based interfaces, the block layer took
care of ensuring that a status request never exceeded 2G in
the driver; but after that conversion, the block layer expects
drivers to deal with any size request (the driver can always
truncate the request size back down, as long as it makes
progress).  So, in the off-chance that someone makes a large
request, we are at the mercy of whether iscsi_get_lba_status_task()
will cap things to at most INT_MAX / iscsilun->block_size when
it populates lbasd->num_blocks; since I could not easily audit
that, it's better to be safe than sorry by just forcing a 64-bit
multiply.

Fixes: 92809c36
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180508212718.1482663-1-eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
(cherry picked from commit 8ee1cef4593a7bda076891470c0620e79333c0d0)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/iscsi.c b/block/iscsi.c
index f5aecfc8834bc1c397bdd0db2855f36b1a660a84..871947feae1f8aeacd551ba9c075f64ba50769e2 100644 (file)
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -732,7 +732,7 @@ retry:
         goto out_unlock;
     }
 
-    *pnum = lbasd->num_blocks * iscsilun->block_size;
+    *pnum = (int64_t) lbasd->num_blocks * iscsilun->block_size;
 
     if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
         lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {