diff --git a/sys/dev/mlx5/mlx5_core/mlx5_cmd.c b/sys/dev/mlx5/mlx5_core/mlx5_cmd.c
--- a/sys/dev/mlx5/mlx5_core/mlx5_cmd.c
+++ b/sys/dev/mlx5/mlx5_core/mlx5_cmd.c
@@ -1113,11 +1113,16 @@
 
 		block = mlx5_fwp_get_virt(msg, i * MLX5_CMD_MBOX_SIZE);
 
-		memset(block, 0, MLX5_CMD_MBOX_SIZE);
-
 		if (i != (n - 1)) {
+			memset(block, 0, MLX5_CMD_MBOX_SIZE);
+
 			u64 dma = mlx5_fwp_get_dma(msg, (i + 1) * MLX5_CMD_MBOX_SIZE);
 			block->next = cpu_to_be64(dma);
+		} else {
+			/* Zero the rest of the page to satisfy KMSAN. */
+			memset(block, 0, MLX5_ADAPTER_PAGE_SIZE -
+			    (i % MLX5_NUM_CMDS_IN_ADAPTER_PAGE) *
+			    MLX5_CMD_MBOX_SIZE);
 		}
 		block->block_num = cpu_to_be32(i);
 	}
@@ -1508,6 +1513,7 @@
 	}
 	cmd->dma = mlx5_fwp_get_dma(cmd->cmd_page, 0);
 	cmd->cmd_buf = mlx5_fwp_get_virt(cmd->cmd_page, 0);
+	memset(cmd->cmd_buf, 0, MLX5_ADAPTER_PAGE_SIZE);
 	return (0);
 
 failure_alloc_page: