[PATCH for-5.2] block/export/vhost-user-blk-server.c: Avoid potential integer overflow

[Peter Maydell]

In vu_blk_discard_write_zeroes(), we read a 32-bit sector count from
the descriptor and convert it to a 64-bit byte count. Coverity warns
that the left shift is done with 32-bit arithmetic so it might
overflow before the conversion to 64-bit happens. Add a cast to
avoid this.

Fixes: Coverity CID 1435956
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Tested with 'make check' and 'make check-acceptance' only.
---
 block/export/vhost-user-blk-server.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/export/vhost-user-blk-server.c 
b/block/export/vhost-user-blk-server.c
index 62672d1cb95..e5749451e65 100644
--- a/block/export/vhost-user-blk-server.c
+++ b/block/export/vhost-user-blk-server.c
@@ -70,7 +70,7 @@ vu_blk_discard_write_zeroes(BlockBackend *blk, struct iovec 
*iov,
     }
 
     uint64_t range[2] = { le64_to_cpu(desc.sector) << 9,
-                          le32_to_cpu(desc.num_sectors) << 9 };
+                          (uint64_t)le32_to_cpu(desc.num_sectors) << 9 };
     if (type == VIRTIO_BLK_T_DISCARD) {
         if (blk_co_pdiscard(blk, range[0], range[1]) == 0) {
             return 0;
-- 
2.20.1