RDMA/irdma: Check return value from ib_umem_find_best_pgsz

iwmr->page_size stores the return from ib_umem_find_best_pgsz and maybe
zero when used in ib_umem_num_dma_blocks thus causing a divide by zero
error.

Fix this by erroring out of irdma_reg_user when 0 is returned from
ib_umem_find_best_pgsz.

Link: https://lore.kernel.org/r/20210622175232.439-3-tatyana.e.nikolova@intel.comReported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1505149 ("Integer handling issues")
Fixes: b48c24c2 ("RDMA/irdma: Implement device supported verb APIs")
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Tatyana Nikolova <tatyana.e.nikolova@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/irdma/verbs.c

@@ -2783,10 +2783,16 @@ static struct ib_mr *irdma_reg_user_mr(struct ib_pd *pd, u64 start, u64 len,
 	iwmr->ibmr.iova = virt;
 	iwmr->page_size = PAGE_SIZE;
 
-	if (req.reg_type == IRDMA_MEMREG_TYPE_MEM)
+	if (req.reg_type == IRDMA_MEMREG_TYPE_MEM) {
 		iwmr->page_size = ib_umem_find_best_pgsz(region,
 							 SZ_4K | SZ_2M | SZ_1G,
 							 virt);
+		if (unlikely(!iwmr->page_size)) {
+			kfree(iwmr);
+			ib_umem_release(region);
+			return ERR_PTR(-EOPNOTSUPP);
+		}
+	}
 	iwmr->len = region->length;
 	iwpbl->user_base = virt;
 	palloc = &iwpbl->pble_alloc;